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New Delhi metallo-β-lactamase (NDM-1): An update
Abstract
New Delhi metallo-β-lactamase (NDM-1) is a novel broad spectrum carbapenemase with ability to inactivate all β-lactams except aztreonam. However, most of the NDM-1-producers also produce aztreonam hydrolysing-β-lactamases thereby making these pathogens absolutely resistant to all β-lactams. The bla(NDM-1) gene encodes a 27.5 kDa protein of 269 amino acids. It shares very little identity with other metallo-β-lactamases. Maximum identity has been observed to VIM-1/VIM-2 (32.4%). This mini-review is an update of the scientific literature for the said enzyme. Following the recommendation of David livermore, we further propose to combine "aztreonam" and "inhibitor of the most frequently encountered aztreonam hydrolysing-β-lactamases in a given setting" as a possible strategy against NDM-1-producers. The inhibitor should be 'versatile' as well, i.e. it should have the ability to inhibit most of the variants of aztreonam hydrolysing-β-lactamases prevalent in the concerned setting. We strongly recommend surveillance studies using aztreonam/NXL-104-combination against NDM-1-producing pathogens in different geographical regions across the globe.
... The emergence of new infectious diseases has become major source of morbidity and mortality all over the world. The major concern in the recent infectious diseases is the emergence of multi drug-resistant (MDR) bacteria which draws the attention of the community as well as the hospital settings towards developing its treatment strategies (Shakil et al., 2011). ...
... Gram-negative pathogens have been recognized as most problematic bacteria challenges for Infectious Diseases Society of America (Shakil et al., 2011;Boucher et al., 2009). Out of six bacteria, Enterococcus faecium, and Enterobacter species (ESKAPE) pathogens which recognized as particularly troubling, four are gramnegative. ...
... Out of six bacteria, Enterococcus faecium, and Enterobacter species (ESKAPE) pathogens which recognized as particularly troubling, four are gramnegative. Hence the attention of the scientific community has shifted to the resistant gram-negative bacteria (Shakil et al., 2011;Bush et al., 2010;Rice et al., 2008). However several drugs are available for treatment of β-lactam resistant gram-positive bacterial infections like linezolid, tigecycline and daptomycin 1 . ...
Gram negative bacteria are today’s major worldwide health concern because of production hydrolytic enzyme New Delhi Metallo-β-lactamase (NDM-1). The enzyme NDM-1 is responsible for bacterial resistance against almost all the β-lactam antibiotics. Therefore, NDM-1 inhibitors can play an important role against these emerging highly resistant microorganisms. The existing beta lactamase inhibitors are considered ineffective against these superbugs and there is an urgent need for discovery of novel drugs with selective potential. In this study, we illuminate the binding mode of pimarane diterpenes (diaporthein A and diaporthein B) to the NMD-1 by molecular docking. A computational ligand-target docking approach was used to analyze structural complexes of enzyme target with diaportheins. Auto Grid model showed the most energetically favorable binding mode of natural compounds to beta-lactamase. Docked energies for diaporthein A and B were -8.02 and -8.41 kcal/mol, respectively. These outcomes revealed that these ligands could be potential drugs to treat infectious diseases.
... N ew Delhi metallo--lactamase (NDM-1) is a novel carbapenemase that was first identified in a Klebsiella pneumoniae isolate in India in 2008 (1). Since then, it has disseminated at a high rate among Enterobacteriaceae isolates both within the Indian subcontinent and worldwide (2)(3)(4). The treatment options for infections caused by NDM-1-producing isolates are extremely limited, as these enzymes are known to hydrolyze penicillins, cephalosporins, and carbapenems while typically retaining susceptibility to only colistin and tigecycline (2), neither of which has been shown to be a dependable option on the basis of in vitro time-kill data and case reports (5)(6)(7)(8). ...
... Since then, it has disseminated at a high rate among Enterobacteriaceae isolates both within the Indian subcontinent and worldwide (2)(3)(4). The treatment options for infections caused by NDM-1-producing isolates are extremely limited, as these enzymes are known to hydrolyze penicillins, cephalosporins, and carbapenems while typically retaining susceptibility to only colistin and tigecycline (2), neither of which has been shown to be a dependable option on the basis of in vitro time-kill data and case reports (5)(6)(7)(8). Aztreonam is not readily inactivated by metallo--lactamases, including NDM-1, and may represent another potential option for therapy (1,9). ...
... The rate at which the metallo--lactamase NDM-1 has disseminated globally among members of the family Enterobacteriaceae is alarming (2). Without antimicrobials with novel mechanisms of action readily available, evaluation of the potential clinical utility of existing agents for the treatment of infections caused by these resistant pathogens is imperative. ...
Doripenem and ertapenem have demonstrated efficacy against several NDM-1 producing isolates in vivo, despite having high MICs. Herein we sought to further characterize the efficacy profiles of humanized regimens of standard (500mg every 8h) and high-dose, prolonged infusion doripenem (2g every 8h, 4-h inf) and ertapenem 1g IV every 24h, as well as the comparator regimens of ceftazidime 2g every 8h (2-h inf), levofloxacin 500mg every 24h, and aztreonam 2g every 6h (1-h inf) against a wider range of isolates in a murine thigh infection model. An isogenic wild type and NDM-1 producing K. pneumoniae plus eight clinical NDM-1 producing Enterobacteriaceae were tested in immunocompetent and neutropenic models. The wild type strain was susceptible to all agents, while the isogenic NDM-1 strain was resistant to ceftazidime, doripenem, and ertapenem. Clinical NDM-1 strains were resistant to nearly all five agents (two were susceptible to levofloxacin). In immunocompetent mice, all agents demonstrated ≥ 1 log10 CFU reductions after 24h against the isogenic wild type and NDM-1 strains. Minimal efficacy was observed with ceftazidime, aztreonam, and levofloxacin against the clinical NDM-1 strains. However, despite in vitro resistance, ≥ 1 log10 CFU reductions were achieved with high dose, prolonged infusion doripenem and ertapenem for six of eight clinical strains. Slight enhancements in activity were observed for high-dose, prolonged infusion doripenem over standard doses for three of four isolates tested. Similar efficacy observations were noted in neutropenic mice. These data suggest that carbapenems are a viable treatment option for infections caused by NDM-1 producing Enterobacteriaceae.
... Metallo-β-lactamases are more dreadful because of their broad catalytic activity of hydrolyzing β-lactam type antibiotics. New Delhi metallo-β-lactamase-1 is the most prevalent and harmful strain of the metallo-β-lactamases (Khan et al. 2017;Kashyap et al. 2017;Kumarasamy et al. 2010;Shakil et al. 2011). ...
... New Delhi metallo-β-lactamase-1 (NDM-1) NDM-1 (EC 3.5.2.6) is a type of B1 MBL formed in pathogens specially Gram-negative carrying bla NDM-1 gene (Shakil et al. 2011;King et al. 2012). These pathogens are also called "super bugs" or "bad bugs" because they are resistant to all antibiotics including carbapenem and are responsible for severe infections in humans (Talbot 2008;Srivastava et al. 2011). ...
The most common mechanism of the resistance to β-lactam antibiotics is the expIdentification of cisplatin and palladiuression of β-lactamases, which can hydrolyze the β-lactam moiety and deactivate these antimicrobials. The worldwide prevalence of New Delhi metallo-β-lactamase-1 (NDM-1), also known as carbapenemase has created distress among clinicians. NDM-1 is a type of metallo β-lactamase (type of β-lactamases which require metal ions for their catalytic action) produced in pathogens carrying blaNDM-1 gene. These NDM-1 producing pathogens are resistant to all β-lactam antibiotics including carbapenems and are greatest threat to public health as they can easily extend via horizontal gene transfer. Various NDM-1 variants have been evolved over time and it may further evolve in the future due to several factors such as bacterial gene mutation and overuse of antibiotics. In the past 10 years, various NDM-1 inhibitors have been reported showing diverse chemical structure. In spite of a great development in terms of structural and mechanistic information, the design of a potent inhibitor of NDM-1 to be approved clinically remains challenging, this could be due to structural complexity of the enzyme that limits the development of clinically useful NDM-1 inhibitors. Along with designing of novel and effective NDM-1 inhibitors, measures should be taken for controlling multidrug resistance. Currently, there is non-availability of NDM-1 inhibitors clinically therefore clinicians are facing a huge challenge in treating infections due to multidrug-resistant bacteria. This review article has been planned to discuss about antibiotic resistance, NDM-1, mechanism of antibiotic resistance by NDM-1, and recent updates in the development of NDM-1 inhibitors as well as mechanism of action of NDM-1 inhibitors.
... Global reports of infections by New Delhi metallo-ß-lactamase 1 (NDM-1)-producing Klebsiella pneumonia are increasing; the β-lactamase produced by this strain is particularly worrying, as it is able to inactive all β-lactams, with the exception of aztreonam [1]. NDM-1-producing Klebsiella pneumonia was first identified in India in 2008, and has since disseminated at a high rate among Enterobacteriaceae isolates in India and other countries [2][3][4]. These NDM-1-producing strains are a source of community-acquired urinary tract and nosocomial infections, which can result in serious septicaemia and ventilator associated pneumonia (VAP) [1]. ...
... These NDM-1-producing strains are a source of community-acquired urinary tract and nosocomial infections, which can result in serious septicaemia and ventilator associated pneumonia (VAP) [1]. At present, drugs capable of treating infections caused by NDM-1-producing Klebsiella pneumonia are limited to colistin and tigecycline [2]. Another bacterial species, Acinetobacter baumannii, is known for its ability to cause hospital infections and its resistance to most antibiotics [5]. ...
This study was designed to investigate the antimicrobial activity of two synthetic antimicrobial peptides from an aquatic organism, tilapia piscidin 3 (TP3) and tilapia piscidin 4 (TP4), in vitro and in a murine sepsis model, as compared with ampicillin, tigecycline, and imipenem. Mice were infected with (NDM-1)-producing K. pneumonia and multi-drug resistant Acinetobacter baumannii, and subsequently treated with TP3, TP4, or antibiotics for different periods of time (up to 168 h). Mouse survival and bacterial colony forming units (CFU) in various organs were measured after each treatment. Toxicity was determined based on observation of behavior and measurement of biochemical parameters. TP3 and TP4 exhibited strong activity against K. pneumonia and A. baumannii in vitro. Administration of TP3 (150 μg/mouse) or TP4 (50 μg/mouse) 30 min after infection with K. pneumonia or A. baumannii significantly increased survival in mice. TP4 was more effective than tigecycline at reducing CFU counts in several organs. TP3 and TP4 were shown to be non-toxic, and did not affect mouse behavior. TP3 and TP4 are able at potentiate anti-Acinetobacter baumannii or anti-Klebsiella pneumonia drug activity, reduce bacterial load, and prevent drug resistance, indicating their potential for use in combating multidrug-resistant bacteria.
... However, there are two major limitations for their use. First, there are no published clinical data, and second, many of the Enterobacteriaceae isolates that produce MBLs or oxacillinases additionally carry ESBLs or other resistant determinants that confer resistance to aztreonam and extendedexpectrum cephalosporins [Falagas et al. 2011;Shakil et al. 2011]. For isolates coexpressing ESBLs and MBLs, a combination of aztreonam with a b-lactamase inhibitor has been proposed [Shakil et al. 2011;Livermore et al. 2011a]. ...
... First, there are no published clinical data, and second, many of the Enterobacteriaceae isolates that produce MBLs or oxacillinases additionally carry ESBLs or other resistant determinants that confer resistance to aztreonam and extendedexpectrum cephalosporins [Falagas et al. 2011;Shakil et al. 2011]. For isolates coexpressing ESBLs and MBLs, a combination of aztreonam with a b-lactamase inhibitor has been proposed [Shakil et al. 2011;Livermore et al. 2011a]. ...
Enterobacteriaceae showing resistance to cephalosporins due to extended-spectrum β-lactamases (ESBLs) or plasmid-mediated AmpC enzymes, and those producing carbapenemases have spread worldwide during the last decades. Many of these isolates are also resistant to other first-line agents such as fluoroquinolones or aminoglycosides, leaving few available options for therapy. Thus, older drugs such as colistin and fosfomycin are being increasingly used. Infections caused by these bacteria are associated with increased morbidity and mortality compared with those caused by their susceptible counterparts. Most of the evidence supporting the present recommendations is from in vitro data, animal studies, and observational studies. While carbapenems are considered the drugs of choice for ESBL and AmpC producers, recent data suggest that certain alternatives may be suitable for some types of infections. Combined therapy seems superior to monotherapy in the treatment of invasive infections caused by carbapenemase-producing Enterobacteriaceae. Optimization of dosage according to pharmacokinetics/pharmacodynamics data is important for the treatment of infections caused by isolates with borderline minimum inhibitory concentration due to low-level resistance mechanisms. The increasing frequency and the rapid spread of multidrug resistance among the Enterobacteriaceae is a true and complex public health problem.
... The most prevalent MBLs globally are variants of NDM, VIM, and Imipenemase (IMP) [12][13][14][15]. There has been successful progress in developing several FDA-approved SBLIs for clinical use [16][17][18][19][20]. ...
Virulent Enterobacterale strains expressing serine and metallo-β-lactamases (MBL) genes have emerged responsible for conferring resistance to hard-to-treat infectious diseases. One strategy that exists is to develop β-lactamase inhibitors to counter this resistance. Currently, serine β-lactamase inhibitors (SBLIs) are in therapeutic use. However, an urgent global need for clinical metallo-β-lactamase inhibitors (MBLIs) has become dire. To address this problem, this study evaluated BP2, a novel beta-lactam-derived β-lactamase inhibitor, co-administered with meropenem. According to the antimicrobial susceptibility results, BP2 potentiates the synergistic activity of meropenem to a minimum inhibitory concentration (MIC) of ≤1 mg/L. In addition, BP2 is bactericidal over 24 h and safe to administer at the selected concentrations. Enzyme inhibition kinetics showed that BP2 had an apparent inhibitory constant (Ki app) of 35.3 µM and 30.9 µM against New Delhi Metallo-β-lactamase (NDM-1) and Verona Integron-encoded Metallo-β-lactamase (VIM-2), respectively. BP2 did not interact with glyoxylase II enzyme up to 500 µM, indicating specific (MBL) binding. In a murine infection model, BP2 co-administered with meropenem was efficacious, observed by the >3 log10 reduction in K. pneumoniae NDM cfu/thigh. Given the promising pre-clinical results, BP2 is a suitable candidate for further research and development as an (MBLI).
Keywords:
metallo-β-lactamases; Carbapenem resistant Enterobacterales; cyclic amino acidic chelator; BP2; murine thigh infection model
... The broad substrate spectrum of KPC enzyme covers all beta-lactam classes, including nitrocefin, cefotaxime, cephalothin, cephaloridine, benzylpenicillin, ampicillin and piperacillin. 5 NDM is known to inactivate all β-lactams except aztreonam, 30 which explained why KP2 and KP4 were sensitive to aztreonam in the antimicrobial test. ...
Background:
The rising prevalence of infections caused by carbapenem-resistant and hypervirulent Klebsiella pneumoniae (CR-hvKP) has outpaced our understanding of their evolutionary diversity. By straining the antimicrobial options and constant horizontal gene transfer of various pathogenic elements, CR-hvKP poses a global health threat.
Methods:
Six KP isolates (KP1~KP6) from urine, sputum and groin infection secretion of a single patient were characterized phenotypically and genotypically. The antimicrobial susceptibility, carbapenemase production, hypermucoviscosity, serum resistance, virulence factors, MLST and serotypes were profiled. Genomic variations were identified by whole-genome sequencing and the phylogenetic differentiation was analyzed by Enterobacterial repetitive intergenic consensus (ERIC)-PCR.
Results:
All KP strains were multi-drug resistant. Four of them (KP1, KP3, KP5 and KP6) belonged to ST11-K64, with high genetic closeness (relatedness coefficient above 0.96), sharing most resistance and virulence genes. Compared with KP1, the later isolates KP3, KP5 and KP6 acquired bla KPC-1 and lost bla SHV-182 genes. KP2 and KP4 had the same clonal origin of ST35-K16 (relatedness coefficient 0.98), containing almost identical genes for resistance and virulence. They were non-mucoid and carried bla NDM-5 gene.
Conclusion:
A co-infection with two types of CR-hvKP affiliated with different clades within a single patient amplified the treatment difficulties. In addition to source control and epidemiological surveillance, investigation of the in-host interactions between CR-hvKP variants may provide valuable treatment solutions.
... Since conventional phenotypic methods failed to detect serine carbapenemase and MbL coproduction, we tested modifications of the DDST and CDT methods based on use of avibactam, EDTA, and DPA as inhibitors, with aztreonam and ceftazidime-avibactam as enzymatic substrates. These modifications were carried out considering that MbLs (including NDM-1) are susceptible to aztreonam and are inhibited by EDTA or DPA (11,26), whereas KPC-2 serine carbapenemases are susceptible to CZA and are inhibited by AVI (27). Indeed, we observed that Klebsiella isolates coproducing KPC-2 and NDM-1 displayed a positive CDT, with $4-mm inhibition zones around CZA 50 with DPA or CZA 50 with EDTA disks and $5-mm inhibition zones around ATM-AVI disks containing 4 mg/mL AVI. ...
Reports of Gram-negative bacteria harboring multiple carbapenemase genes have increased in South America, leading to an urgent need for appropriate microbiological diagnosis. We evaluated phenotypic methods for detecting Klebsiella pneumoniae carbapenemase 2 (KPC-2) and New Delhi metallo-b-lactamase-1 (NDM-1) coexpression in
members of the K. pneumoniae complex (i.e., K. pneumoniae, K. quasipneumoniae, and K. variicola) isolated from human and animal hosts, based on inhibition of ceftazidime-avibactam (CZA) and aztreonam (ATM) by dipicolinic acid (DPA), EDTA, or avibactam (AVI).
While the presence of blaKPC-2 and blaNDM-1 genes was confirmed by whole-genome sequencing, PCR, and/or GeneXpert, coexpression was successfully detected based on the following: (i) a 5-mm increase in the zone diameter of ATM (30 µg) disks plus AVI (4 or 20 µg) and 4-mm and 10-mm increases in the zone diameters for “CZA 50” (30 µg ceftazidime [CAZ] and 20 µg AVI) and “CZA 14” (10 µg CAZ and 4 µg AVI) disks, respectively, when we added DPA (1 mg/disk) or EDTA (5 mM) in a combined disk test (CDT); (ii) a positive ghost zone (synergism) between ATM (30 µg) and CZA 50 disks and between CZA 50 and DPA (1 mg) disks, using the double-disk synergy test (DDST) at a disk-disk distance of 2.5 cm; (iii) 3-fold MIC reductions of ATM and CZA in the presence of AVI (4 µg/mL), DPA (500 mg/mL), or EDTA (320 µg/mL); and (iv) immunochromatography. Although our results demonstrated that inhibition by AVI, DPA, and EDTA may provide simple and inexpensive methods for the presumptive detection of coexpression of KPC-2 and NDM-1 in members of the K. pneumoniae complex, additional studies are necessary to confirm the accuracy of these methodologies by testing other Gram-negative bacterial species and other KPC and NDM variants coexpressed by WHO critical priority pathogens detected worldwide.
... The parental strain Kp17 was highly resistant to ceftazidime-avibactam because avibactam is unable to inhibit NDM-1 (27). However, Kp17 was susceptible to aztreonam/avibactam, which might be due to the resistance of aztreonam to NDM-1 (28). Interestingly, all the evolved eravacycline-resistant strains displayed a 2-fold reduction in the MIC of aztreonam/avibactam (Table S8 in Supplemental File 1). ...
The increasing bacterial antibiotic resistance is a serious threat to global public health, which demands novel antimicrobial medicines and treatment strategies. Eravacycline is a newly approved antibiotic that belongs to the tetracycline antibiotics.
... After the NDM-1 first report, variants of this enzyme emerged in the world and it became a global concern 7 . Furthermore, most plasmids carrying the NDM-1 gene often associate to other resistance genes, such as sulfonamides, rifampin, chloramphenicol, quinolones, and macrolides 8,9 . This property converts NDM-1 carrying bacteria to multi-drug resistant bacteria. ...
New Delhi metallo-β-lactamase variants and different types of metallo-β-lactamases have attracted enormous consideration for hydrolyzing almost all β-lactam antibiotics, which leads to multi drug resistance bacteria. Metallo-β-lactamases genes have disseminated in hospitals and all parts of the world and became a public health concern. There is no inhibitor for New Delhi metallo-β-lactamase-1 and other metallo-β-lactamases classes, so metallo-β-lactamases inhibitor drugs became an urgent need. In this study, multi-steps virtual screening was done over the NPASS database with 35,032 natural compounds. At first Captopril was extracted from 4EXS PDB code and use as a template for the first structural screening and 500 compounds obtained as hit compounds by molecular docking. Then the best ligand, i.e. NPC120633 was used as templet and 800 similar compounds were obtained. As a final point, ten compounds i.e. NPC171932, NPC100251, NPC18185, NPC98583, NPC112380, NPC471403, NPC471404, NPC472454, NPC473010 and NPC300657 had proper docking scores, and a 50 ns molecular dynamics simulation was performed for calculation binding free energy of each compound with New Delhi metallo-β-lactamase. Protein sequence alignment, 3D conformational alignment, pharmacophore modeling on all New Delhi metallo-β-lactamase variants and all types of metallo-β-lactamases were done. Quantum chemical perspective based on the fragment molecular orbital (FMO) method was performed to discover conserved and crucial residues in the catalytic activity of metallo-β-lactamases. These residues had similar 3D coordinates of spatial location in the 3D conformational alignment. So it is posibble that all types of metallo-β-lactamases can inhibit by these ten compounds. Therefore, these compounds were proper to mostly inhibit all metallo-β-lactamases in experimental studies.
... After the NDM-1 rst report, variants of this enzyme emerged in the world and it became a global concern [7]. Furthermore, most plasmids carrying the NDM-1 gene often associated with other resistance genes, such as sulfonamides, rifampin, chloramphenicol, quinolones, and macrolides [8,9]. This property converts NDM-1 carrying bacteria to multi-drug resistant bacteria. ...
New Delhi metallo-β-lactamase variants and different types of metallo-β-lactamases have attracted enormous consideration for hydrolyzing almost all β-lactam antibiotics, which leads to multi drug resistance bacteria. Metallo-β-lactamases genes have disseminated in hospitals and all parts of the world and became a public health concern. There is no inhibitor for new Delhi metallo-β-lactamase-1 and other metallo-β-lactamases classes, so metallo-β-lactamases inhibitor drugs became an urgent need. In this study, multi-steps virtual screening was done over the NPASS database with 35032 natural compounds.
At first Captopril was extracted from 4EXS PDB code and use as a template for the first structural screening and 500 compounds obtained as hit compounds by molecular docking. Then the best ligand, i.e. NPC120633 was used as templet and 800 similar compounds were obtained. As a final point, ten compounds i.e. NPC171932, NPC100251, NPC18185, NPC98583, NPC112380, NPC471403, NPC471404, NPC472454, NPC473010 and NPC300657 had proper docking scores, and a 50 ns molecular dynamics simulation was performed for calculation binding free energy of each compound with new Delhi metallo-β-lactamase. 3D conformational alignment and protein sequence alignment of all new Delhi metallo-β-lactamase variants and all types of metallo-β-lactamases were done. Then the conserved and crucial residues in the catalytic activity of metallo-β-lactamases were detected. These residues had similar 3D coordinates in the 3D conformational alignment. So it is possible that all types of metallo-β-lactamases can inhibit by these ten compounds. Therefore, these compounds were proper to mostly inhibit all new Delhi metallo-β-lactamase and metallo-β-lactamases in experimental studies.
... Currently, K. pneumoniae with OXA-48-like carbapene mases are spreading rapidly in many European countries, in addition to being endemic in the Middle East and in Northern Africa [1,4,5]. Bacteria with the New Delhi metallo-β-lactamase (NDM) enzyme, which was first identified in Sweden from a patient who had travelled from New Delhi, India, have attained endemic levels in countries of the Indian subcontinent including India, Pakistan, Bangladesh and Sri Lanka [1,[4][5][6][7][8]. This gene is also encountered in bacteria, including K. pneumoniae, in some countries in the South East Asian region, including Singapore [9], Thailand [10] and Vietnam [1]. ...
Objective:
A prospective observational study was performed to assess the epidemiology and clinical impact of carbapenem-non-susceptible Klebsiella pneumoniae (CNKP) in intensive care units (ICUs) of the national referral hospital in Jakarta, Indonesia.
Materials/methods:
Adult patients consecutively hospitalized for > 48 h in two ICUs of the national referral hospital were included from April until October 2013 and from April until August 2014. K. pneumoniae from clinical cultures and standardized screening of rectum and throat on admission, discharge and weekly if hospitalized > 7 days were collected. Environmental niches and healthcare workers (HCWs) were also screened. Susceptibility was determined phenotypically and the presence of carbapenemase genes by PCR. Raman spectroscopy as well as multiple-locus variable number tandem repeat analysis (MLVA) were used for typing.
Results:
Twenty-two out of 412 (5.3%) patients carried CNKP on admission and 37/390 (9.5%) acquired CNKP during ICU stay. The acquisition rate was 24.7/1000 patient-days at risk. One out of 31 (3.2%) environmental isolates was a CNKP. None of the HCWs carried CNKP. Acquisition of CNKP was associated with longer ICU stay (adjusted Hazard Ratio: 2.32 [CI99: 1.35-3.68]). ICU survival was lower among patients with CNKP compared to patients with carbapenem-susceptible K. pneumoniae (aHR 2.57, p = 0.005). Ninety-six of the 100 (96%) CNKP isolates carried a carbapenemase gene, predominantly blaNDM. Raman typing revealed three major clusters among 48 Raman types identified, whereas MLVA distinguished six major clusters among a total of 30 different genotypes.
Conclusions:
NDM-producing CNKP are introduced into these ICUs and some strains expand clonally among patients and the environment, resulting in endemic CNKP. CNKP acquisition was associated with prolonged ICU stay and may affect ICU survival.
Trial registration:
The study was registered at Netherlands Trial Register http://www.trialregister.nl. Candidate number: 23527, NTR number: NTR5541, NL number: NL5425 (https://www.trialregister.nl/trial/5424), Retrospectively registered: NTR: 22 December 2015.
... 18,20 However, recent strains that carry the bla NDM-1 gene are also aztreonam resistant, probably by a different resistance mechanism. 21 Significant strategies have been reported in recent years for the development of MBL inhibitors, but none of them have reached the clinic. 22,23 One efficient strategy to combat resistance is combination therapy with an antibiotic and a potentiator that enhances the antibiotic's activity by overcoming the bacterial resistance mechanisms. ...
New Delhi Metallo-β-lactamase-1 (NDM-1) is the major contributor to the emergence of carbapenem-resistance in Gram-negative pathogens (GNPs) and has caused many clinically available β-lactam antibiotics to become obsolete. A clinically approved inhibitor of metallo-β-lactamase (MBL) that could restore the activity of carbapenems against resistant GNPs has not yet been found, making NDM-1 a serious threat to human health. Here, we have rationally developed an inhibitor for the NDM-1 enzyme, which has the ability to penetrate the outer membrane of GNPs and inactivate the enzyme by depleting the metal ion (Zn2+) from the active site. The inhibitor reinstated the activity of meropenem against NDM-1 producing clinical isolates of GNPs like Klebsiella pneumoniae and Escherichia coli. Further, the inhibitor efficiently restored meropenem activity against NDM-1 producing K. pneumoniae in a murine sepsis infection model. These findings demonstrate that a combination of the present inhibitor and meropenem has high potential to be translated clinically to combat carbapenem-resistant GNPs.
... However, many strains harbouring the bla NDM gene on plasmids are also aztreonam-resistant due to the production of additional aztreonam-hydrolysing b-lactamases, resulting in absolute b-lactam resistance [3]. Multiple resistance determinants on plasmids bearing the bla NDM gene confer extensive drug resistance to these isolates, thus limiting therapeutic options [4]. ...
... However, resistance to carbapenems can occur and is often multifactorial, arising from the synergistic effects of a decrease in the expression of outermembrane porins (OMP) that facilitate carbapenem entry into cells; the overexpression of tripartite pumps, responsible for carbapenem extrusion; and, most importantly, the production of metallo-β-lactamases, which can degrade carbapenems [18,73,74]. Indeed, Enterobacteriacaea, such as Klebsiella pneumonia, that can produce metallo-β-lactamases, such as NDM-1 The var antibiotic resistance regulon [75], have emerged worldwide as important pathogens of nosocomial infections because of the difficulty in treating the infections they cause [16,72]. Carbapenems are also an important therapeutic for treating infections due to Pseudomonas aeruginosa, because they are effective when other β-lactams are not due to production of the serine β-lactamase AmpC [76]. ...
The genome sequence of V. cholerae O1 Biovar Eltor strain N16961 has revealed a putative antibiotic resistance (var) regulon that is predicted to encode a transcriptional activator (VarR), which is divergently transcribed relative to the putative resistance genes for both a metallo-β-lactamase (VarG) and an antibiotic efflux-pump (VarABCDEF). We sought to test whether these genes could confer antibiotic resistance and are organised as a regulon under the control of VarR. VarG was overexpressed and purified and shown to have β-lactamase activity against penicillins, cephalosporins and carbapenems, having the highest activity against meropenem. The expression of VarABCDEF in the Escherichia coli (ΔacrAB) strain KAM3 conferred resistance to a range of drugs, but most significant resistance was to the macrolide spiramycin. A gel-shift analysis was used to determine if VarR bound to the promoter regions of the resistance genes. Consistent with the regulation of these resistance genes, VarR binds to three distinct intergenic regions, varRG, varGA and varBC located upstream and adjacent to varG, varA and varC, respectively. VarR can act as a repressor at the varRG promoter region; whilst this repression was relieved upon addition of β-lactams, these did not dissociate the VarR/varRG-DNA complex, indicating that the de-repression of varR by β-lactams is indirect. Considering that the genomic arrangement of VarR-VarG is strikingly similar to that of AmpR-AmpC system, it is possible that V. cholerae has evolved a system for resistance to the newer β-lactams that would prove more beneficial to the bacterium in light of current selective pressures.
... β-lactamase inhibitors such as NXL 104 may inhibit the activity of extended spectrum β-lactamases that are mostly present in NDM-1 producers (Livermore et al., 2011a;Shakil et al., 2011). ...
One of the most recent and most clinically significant carbapenemases is New Delhi metallo- ß-lactamase (NDM-1). Among the NDM-1-producing Enterobacteriaceae, Klebsiella pneumoniae and Escherichia coli were the most often described species. NDM-1, like all metallo-ß-lactamases (MBLs), confers resistance to a broad range of ß-lactams, including penicillins, cephalosporins, and carbapenems. Carba NP test has been developed to rapidly identify the different carbapenemase types found in Enterobacteriaceae and P. aeruginosa, and further ongoing developments of the test may lead to its use for carbapenemase producers in A. baumannii. The prevention of the spread of carbapenemase producers relies on an early and accurate detection of carriers in hospital units or on admission/discharge, either in a hospital or in a specific unit. The chapter explains why the outbreak of NDM producers is much more serious than an outbreak with other carbapenemase producers (KPC) that remain mostly in nosocomial-acquired K. pneumoniae pathogens.
... La Nueva Delhi metalo-β-lactamasa (NDM) es una carbapenemasa adquirida de clase B, inicialmente reportada en un paciente suizo en un hospital de Nueva Delhi, India, que confiere resistencia a todos los b-lactámicos 1,3 . Aunque algunos reportes indican que la NDM no hidroliza monobactámicos, la mayoría de cepas productoras de NDM también expresan enzimas que podrían hidrolizar monobactámicos, haciendo a estas muy difíciles de controlar 3,4 . ...
Notificamos un caso de infección por Escherichia coli productora de Nueva Delhi metalo-b-lactamasa (NDM) en un paciente que desarrolló un absceso subcapsular hepático como complicación de una colecistectomía laparoscópica. La NDM es una carbapenemasa adquirida tipo Ambler B, que confiere resistencia a todos los b-lactámicos, excepto al aztreonam, aunque existen reportes de resistencia a este último. En Colombia, la primera descripción de cepas productoras de NDM se realizó en aislamientos de Klebsiella pneumoniae en una unidad de cuidados intensivos neonatales en Bogotá. Desde entonces se han realizado reportes de distintas cepas, siendo esta la primera reportada en el país relacionada con Escherichia coli productora de NDM.
... Contrary to the New Delhi metallo-β -lactamase, which is a broad spectrum carbapenemase with ability to inactivate β -lactams except aztreonam 35 , all carabapenem resistant isolates in our study were also resistant to aztreonem. This may be due to the development of a new antimicrobial resistance pattern in Egyptian hospitals. ...
Klebsiella pneumonia infection rates have increased dramatically. Molecular typing and virulence analysis are powerful tools that can shed light on Klebsiella pneumonia infections. Whereas 77.7% (28/36) of clinical isolates indicated multidrug resistant (MDR) patterns, 50% (18/36) indicated carpabenem resistance. Gene prevalence for the AcrAB efflux pump (82.14%) was more than that of the mdtK efflux pump (32.14%) in the MDR isolates. FimH-1 and mrkD genes were prevalent in wound and blood isolates. FimH-1 gene was prevalent in sputum while mrkD gene was prevalent in urine. Serum resistance associated with outer membrane protein coding gene (traT) was found in all blood isolates. IucC, entB, and Irp-1 were detected in 32.14%, 78.5% and 10.7% of MDR isolates, respectively. We used two Polymerase Chain Reaction (PCR) analyses: Enterobacterial Repetitive Intergenic Consensus (ERIC) and Random Amplified Polymorphic DNA (RAPD). ERIC-PCR revealed 21 and RAPD-PCR revealed 18 distinct patterns of isolates with similarity ≥80%. ERIC genotyping significantly correlated with resistance patterns and virulence determinants. RAPD genotyping significantly correlated with resistance patterns but not with virulence determinants. Both RAPD and ERIC genotyping methods had no correlation with the capsule types. These findings can help up better predict MDR Klebsiella pneumoniae outbreaks associated with specific genotyping patterns.
... The monobactam aztreonam is resistant to inactivation by NDM, but not serine -lactamases. Accordingly, high levels of NDM and serine -lactamase co-occurrence reduces the clinical utility of aztreonam monotherapy (Shakil et al., 2011). An aztreonam-avibactam combination inhibited 99.9% (n = 23,516) of Enterobacteriaceae species at 4/4 g/ml. ...
Carbapenems, our one-time silver bullet for multidrug resistant bacterial infections, are now threatened by widespread dissemination of carbapenem-resistant Enterobacteriaceae (CRE). Successful expansion of Enterobacteriaceae clonal groups and frequent horizontal gene transfer of carbapenemase expressing plasmids are causing increasing carbapenem resistance. Recent advances in genetic and phenotypic detection facilitate global surveillance of CRE diversity and prevalence. In particular, whole genome sequencing enabled efficient tracking, annotation, and study of genetic elements colocalized with carbapenemase genes on chromosomes and on plasmids. Improved characterization helps detail the co-occurrence of other antibiotic resistance genes in CRE isolates and helps identify pan-drug resistance mechanisms. The novel β-lactamase inhibitor, avibactam, combined with ceftazidime or aztreonam, is a promising CRE treatment compared to current colistin or tigecycline regimens. To halt increasing CRE-associated morbidity and mortality, we must continue quality, cooperative monitoring and urgently investigate novel treatments.
... La Nueva Delhi metalo--lactamasa (NDM) es una carbapenemasa adquirida de clase B, inicialmente reportada en un paciente suizo en un hospital de Nueva Delhi, India, que confiere resistencia a todos los -lactámicos 1,3 . Aunque algunos reportes indican que la NDM no hidroliza monobactámicos, la mayoría de cepas productoras de NDM también expresan enzimas que podrían hidrolizar monobactámicos, haciendo a estas muy difíciles de controlar 3,4 . ...
Notificamos un caso de infección por Escherichia coli productora de Nueva Delhi metalo-β-lactamasa (NDM) en un paciente que desarrolló un absceso subcapsular hepático como complicación de una colecistectomía laparoscópica. La NDM es una carbapenemasa adquirida tipo Ambler B, que confiere resistencia a todos los β-lactámicos, excepto al aztreonam, aunque existen reportes de resistencia a este último. En Colombia, la primera descripción de cepas productoras de NDM se realizó en aislamientos de Klebsiella pneumoniae en una unidad de cuidados intensivos neonatales en Bogotá. Desde entonces se han realizado reportes de distintas cepas, siendo esta la primera reportada en el país relacionada con Escherichia coli productora de NDM.
... In particular to cefuraxime cefotaxime, and cephalothin and also to the penicillins (Shakil et al., 2011).However, it does not bind to carbapenem as tightly as IMP-1 or VIM-2 (Yong et al., 2009). ...
This study analyzed the prevalence of carbapenem resistance in clinical isolates of Klebsiella
pneumoniae.
During the period from April to August 2011, a total of 801 various clinical samples were collected
from different hospitals in Hilla city. K.pneumoniae isolates were identified by standard
biochemical tests
,then confirmed by VITEK 2 system . Antibiotic susceptibility profile and minimum inhibitory
concentration (MIC) tests were determined by the disk diffusion and HiComb, Minimum inhibitory
concentration evaluator (M.I.C.E.) methods, respectively. The ability of isolates to produce -
lactamase was determined by iodometric method. Carbapenemase,
extended –spectrum - lactamase (ESBL) and AmpC - lactamase were
initially detected and confirmed by the phenotypic methods. Carbapenemase –encoding genes
(KPC,IMP,VIM,NDM-1, OXA-23 and SME), ESBLs genes (TEM, SHV, CTX-M, OXA-1,VEB,PER and GES)
and AmpC - lactamases (AmpC) were detected by conventional Polymerase chain reaction (PCR)
technique. Conjugation experiments were performed by using rifampicin resistant Escherchia coli
MM294 as a recipient strain.
Out of 801 ,177 Klebsiella spp. isolates were identified .Of
these,117 were specified as K.pneumoniae . High prevalence were detected in Babylon Teaching
Hospital for Maternity and Pediatric 65 (23%) ,followed by Chest Diseases Center 19 (14.8%). All
K.pneumoniae isolates were identified to the level of subspecies. Results revealed that 77
(9.6%),34 (4%) and 6 (1%) were belonged to K.pneumoniae subsp. pneumoniae , K.pneumoniae subsp.
ozaenae and K.pneumoniae subsp rhinoscleromatis, respectively.
... While NDM-1 strains are difficult to treat, many of them remain sensitive to an older, seldom used antibiotic, colistin, or aztreonam [123,124] 85 Years, clinical trial number N C T 0 1 7 0 6 3 6 7 ; a n d S a f e t y, To l e r a b i l i t y, a n d Immunogenicity Study of a Clostridium Difficile Toxoid Vaccine in Healthy Adult Volunteers, clinical trial number NCT00127803 (a total of 15 studies were found on www. clinicaltrials.gov ...
The threat from microorganisms is complex, and the approaches for reducing the challenges the world is facing are also multifaceted, but a combination approach including several simple steps can make a difference and reduce morbidity and mortality and the economic cost of fighting infectious diseases. This paper discusses the continually evolving infectious disease landscape, contributing factors in the rise of the threat, reasons for optimism, and the policies, technologies, actions, and institutions that might be harnessed to further reduce the dangers introduced by pathogens. It builds upon and updates the work of other authors that have recognized the dangers of emerging and re-emerging pathogens and have explored and documented potential solutions.
... The various types of b-lactamases, including the New Delhi metallo-b-lactamase (NDM-1), can rapidly inactivate b-lactams (BLs) and are commonly found in Escherichia coli isolates. 1,2 The plasmid that encodes the NDM-1 can carry other b-lactamase genes, and the concerted expression of several different types of b-lactamases is believed to be the mechanism by which bacteria develop multiple resistances to various BLs. 2 The b-lactamases, when expressed, are able to hydrolyse many of the later-generation cephalosporins. 3 -7 A b-lactamase inhibitor (BLI) is co-administered along with these BLs as a way to restore the efficacy of antimicrobials in resistant bacterial infection. ...
Objectives:
The combination of aztreonam and avibactam has been proposed for the treatment of infections caused by metallo-β-lactamase-producing Gram-negative organisms, given the stability of aztreonam against metallo-β-lactamases plus the broad coverage of avibactam against AmpC β-lactamases and ESBLs. This study aimed to evaluate the efficacy of the combination against four clinical isolates with defined but diverse β-lactamase profiles.
Methods:
The MICs of aztreonam were determined without and with avibactam (1, 2, 4, 8 and 16 mg/L). Using the MIC values, the static time-kill kinetic studies were designed to encompass aztreonam concentrations of 0.25, 0.5, 1, 2 and 4 times the MIC at the respective avibactam concentrations from 0 to 8 mg/L. Aztreonam and avibactam concentrations were determined by LC-MS/MS during the course of the time-kill kinetic studies to evaluate whether avibactam protects aztreonam from degradation.
Results:
Three of the four isolates had aztreonam MICs ≥128 mg/L in monotherapy. Dramatically increasing susceptibility associated with a decrease in aztreonam MIC was observed with increasing avibactam concentration. Against all isolates, the combinations resulted in greater killing with a much lower dose requirement for aztreonam. The resulting changes in base-10 logarithm of cfu/mL at both the 10 h and 24 h references (versus 0 h) were synergistic. In contrast, a significantly higher concentration of aztreonam in the monotherapy was required to produce the same kill as that in the combination therapy, due to rapid aztreonam degradation in two isolates.
Conclusions:
The aztreonam/avibactam combination protects aztreonam from hydrolysis and provides synergy in antimicrobial activity against multiple β-lactamase-expressing strains with a wide MIC range.
... An ARG-ANNOT analysis (13) indicated presence of the metallo--lactamase (MBL) gene bla NDM-1 exclusively in the R2090 chromosome in addition to other putative resistance determinants present in both genomes. The gene bla NDM-1 encodes a broad-spectrum carbapenemase with the capability to inactivate all -lactam antibiotics except aztreonam (14). As previously described, this gene is located on the transposon Tn125 (15,16). ...
Acinetobacter baumannii is an emerging human pathogen causing nosocomial and community-acquired infections. Here, we present the complete genome
sequence of the clinical A. baumannii strain R2090 carrying the metallo-β-lactamase gene blaNDM-1 in its chromosome within the transposon Tn125.
... Contrary to the New Delhi metallo-β -lactamase, which is a broad spectrum carbapenemase with ability to inactivate β -lactams except aztreonam 35 , all carabapenem resistant isolates in our study were also resistant to aztreonem. This may be due to the development of a new antimicrobial resistance pattern in Egyptian hospitals. ...
... New Delhi metallo-β-lactamase (NDM-1) is a serious threat to the existing antibiotic armory [1], and a potent weapon for bacteria to aid in in their 'battle' [2]. After the first report in 2009 [3], NDM-1 became a subject of discussion in scientific as well as political circles, and continues to remain so [4]. ...
New Delhi metallo-β-lactamase (NDM-1) is a serious threat to the existing antibiotic armory, and a potent weapon for bacteria to aid in in their ‘battle’. It has the ability to inactivate all β-lactams, except aztreonam. However, most of the NDM-1-producers also produce aztreonam hydrolysing-β-lactamases, thereby making these pathogens absolutely resistant to all β-lactams. This minireview incorporates a concise update on global epidemiology (2009- 2012) of NDM-1. However, the crux of the discussion is to focus on paucity of clinically useful therapeutic options, and suggest a solution to the drug resistance threat imposed by NDM-1 bacterial enzyme. The manuscript presents a ‘region-specific treatment strategy’ in a lucid flowchart format. The flowchart which lies at the interface of clinical microbiology and bioinformatics is expected to be useful in containing the problem of drug resistance due to NDM- 1-producing bacterial pathogens.
... The emerging NDM-1, an acquired class B carbapenemase that was first clinically detected in a patient at a hospital in New Delhi, India, has brought up worldwide public attention again (Bonomo, 2011;Rolain et al., 2010). Although current reports indicate that NDM-1 does not hydrolyze monobactams, most of NDM-1carrying strains also express enzymes that could hydrolyze monobactams, making NDM-1-producers very difficult to control (Shakil et al., 2011). The rapid dissemination of NDM-1-producing gram-negative species also contributes to this major concern of public health. ...
Carbapenems are therapeutic choice against infections caused by Gram-negative bacilli including strains of Pseudomonas aeruginosa. New Delhi metallo-β-lactamase (NDM-1) is a novel metallo-β-lactamase (MBL).That confers resistance to all β-lactamases. Sporadic cases of NDM-1 positive strains have been reported from different countries. The aim of this study was to determine the possibility of existence of NDM-1 gene among P. aeruginosa isolates collected from Najaf hospitals. Thirty-six carbapenem resistant P. aeruginosa isolates were collected from various clinical samples. The susceptibility to different antibiotics was evaluated by disk diffusion method, MICs of imipenem and meropenem were determined. The bla NDM was detected by PCR. All isolate were multidrug resistance. Two isolates were harbored bla NDM genes. The MICs of isolates to imipenem and meropenem were 4-128 µg/mL and 4-256 µg/mL, respectively. The study concluded that production of MBL enzymes presents an emerging threat of carbapenem resistance among P. aeruginosa in Najaf province. This is the first report of NDM β-lactamase producing P. aeruginosa in Iraq. Introduction Pseudomonas aeruginosa is an important cause of nosocomial infections and has been associated with a wide variety of illnesses in hospitalized patients, especially patients in the intensive care units (Brooks et al., 2007).The clinical strains of P. aeruginosa are usually multidrug resistant to aminoglycosides, fluoroquinolones, ureidopenicillins and third generation cephalosporins. In cases of resistance to β-lactams caused by extended spectrum β-lactamases and AmpC enzyme, carbapenems are often used as the last resort against infections. However, carbapenem-hydrolyzing-β-lactamases of molecular class A, B and D have emerged over the last decade (Strateva &Yordanov 2009). The emerging NDM-1, an acquired class B carbapenemase that was first clinically detected in a patient at a hospital in New Delhi, India, has brought up worldwide public attention again (Bonomo, 2011; Rolain et al., 2010). Although current reports indicate that NDM-1 does not hydrolyze monobactams, most of NDM-1-carrying strains also express enzymes that could hydrolyze monobactams, making NDM-1-producers very difficult to control (Shakil et al., 2011). The rapid dissemination of NDM-1-producing gram-negative species also contributes to this major concern of public health. It has been reported in 50 countries across five continents, in the last 2 years (Bonomo, 2011; Rolain et al., 2010). NDM-1 is detected mainly in Enterobacteriaceae but occasionally in Acinetobacter baumannii, Stenotrophomonas maltophilia and P.aeruginosa (Jovcic et al., 2011).There is no evidence of the emergence of NDM-1-producing Enterobacteriaceae and P.aeruginosa in Iraq at this point. In the present study, we report the first isolation in Najaf of a NDM-1-producing P.aeruginosa.
... Interestingly, the spread of NDM has been underpinned by the extreme mobility of the bla NDM gene itself, which is mediated by an ISAba125 element upstream of the ndm gene rather than by expansion of an epidemic clone of bacteria or plasmid, as seen with the kpc genes 107 . NDM-producing isolates have been found in many species: the genes are located both on plasmids and on the host chromosome and able to move between the two at high frequency 107,133 . Initially, infections with NDM-carrying bacteria were epidemiologically linked to the Indian subcontinent, Balkan states and Middle East 107 . ...
Antibiotic-resistant bacteria that are difficult or impossible to treat are becoming increasingly common and are causing a global health crisis. Antibiotic resistance is encoded by several genes, many of which can transfer between bacteria. New resistance mechanisms are constantly being described, and new genes and vectors of transmission are identified on a regular basis. This article reviews recent advances in our understanding of the mechanisms by which bacteria are either intrinsically resistant or acquire resistance to antibiotics, including the prevention of access to drug targets, changes in the structure and protection of antibiotic targets and the direct modification or inactivation of antibiotics.
... New Delhi metallo-β-lactamase (NDM-1) is a serious threat to the existing antibiotic armory [1], and a potent weapon for bacteria to aid in in their 'battle' [2]. After the first report in 2009 [3], NDM-1 became a subject of discussion in scientific as well as political circles, and continues to remain so [4]. ...
New Delhi metallo-β-lactamase (NDM-1) is a serious threat to the existing antibiotic armory, and a potent
weapon for bacteria to aid in in their ‘battle’. It has the ability to inactivate all β-lactams, except aztreonam. However,
most of the NDM-1-producers also produce aztreonam hydrolysing-β-lactamases, thereby making these pathogens
absolutely resistant to all β-lactams. This minireview incorporates a concise update on global epidemiology (2009-
2012) of NDM-1. However, the crux of the discussion is to focus on paucity of clinically useful therapeutic options,
and suggest a solution to the drug resistance threat imposed by NDM-1 bacterial enzyme. The manuscript presents
a ‘region-specific treatment strategy’ in a lucid flowchart format. The flowchart which lies at the interface of clinical
microbiology and bioinformatics is expected to be useful in containing the problem of drug resistance due to NDM-
1-producing bacterial pathogens.
... This therapeutic option has been demonstrated to be an efficient combination therapy in vitro but is not available on the market yet. 95,96 ...
While antibiotic resistance is quickly rising in Gram-negative bacteria, the recent spread of a new resistance trait, namely, the New Delhi metallo-β-lactamase (NDM-1), represents an important medical issue. This carbapenemase compromises the efficacy of almost all β-lactams, including the last resort carbapenems. The transferable NDM-1 gene is identified in a variety of enterobacterial species, leading to multidrug resistance in Enterobacteriaceae. In particular, NDM-1-producing Klebsiella pneumoniae and Escherichia coli may cause severe nosocomial infections, including urinary tract infections, peritonitis, septicemia, and pulmonary infections. NDM-1 producers are the source of hospital and community-acquired infections, and are very difficult to control. Therapeutic options are limited to colistin, tigecycline, and fosfomycin. The main reservoirs of NDM producers are currently the Indian subcontinent, the Balkan states, and the Middle East. Rapid diagnostic techniques and isolation of infected patients and carriers are the main factors to try to contain this outbreak, which threatens the efficacy of modern medicine.
... Since NDM-1 does not hydrolyze aztreonam, a combination therapy including aztreonam and avibactam (also named NXL-104), a novel serine -lactamase inhibitor inhibiting the most frequent broadspectrum hydrolyzing--lactamases hydrolyzing aztreonam has been suggested as a possible strategy against NDM-1producing Enterobacteriaceae. This therapeutic option seems to be a very efficient combination therapy in vitro [13,14]. ...
The emergence of one of the most recently described carbapenemases, namely, the New Delhi metallo-lactamase (NDM-1), constitutes a critical and growingly important medical issue. This resistance trait compromises the efficacy of almost all lactams (except aztreonam), including the last resort carbapenems. Therapeutical options may remain limited mostly to colistin, tigecycline, and fosfomycin. The main known reservoir of NDM producers is the Indian subcontinent whereas a secondary reservoir seems to have established the Balkans regions and the Middle East. Although the spread of bla NDM-like genes (several variants) is derived mostly by conjugative plasmids in Enterobacteriaceae, this carbapenemase has also been identified in P. aeruginosa and Acinetobacter spp. Acinetobacter sp. may play a pivotal role for spreading bla NDM genes for its natural reservoir to Enterobacteriaceae. Rapid diagnostic techniques (Carba NP test) and screening of carriers are the cornerstone to try to contain this outbreak which threatens the efficacy of the modern medicine.
The most common resistance mechanism to carbapenems is the production of carbapenemases. In 2021, the Pan American Health Organization warned of the emergence and increase in new carbapenemase combinations in Enterobacterales in Latin America. In this study, we characterized four Klebsiella pneumoniae isolates harboring blaKPC and blaNDM from an outbreak during the COVID-19 pandemic in a Brazilian hospital. We assessed their plasmids’ transference ability, fitness effects, and relative copy number in different hosts. The K. pneumoniae BHKPC93 and BHKPC104 strains were selected for whole genome sequencing (WGS) based on their pulsed-field gel electrophoresis profile. The WGS revealed that both isolates belong to ST11, and 20 resistance genes were identified in each isolate, including blaKPC-2 and blaNDM-1. The blaKPC gene was present on a ~56 Kbp IncN plasmid and the blaNDM-1 gene on a ~102 Kbp IncC plasmid, along with five other resistance genes. Although the blaNDM plasmid contained genes for conjugational transfer, only the blaKPC plasmid conjugated to E. coli J53, without apparent fitness effects. The minimum inhibitory concentrations (MICs) of meropenem/imipenem against BHKPC93 and BHKPC104 were 128/64 and 256/128 mg/L, respectively. Although the meropenem and imipenem MICs against E. coli J53 transconjugants carrying the blaKPC gene were 2 mg/L, this was a substantial increment in the MIC relative to the original J53 strain. The blaKPC plasmid copy number was higher in K. pneumoniae BHKPC93 and BHKPC104 than in E. coli and higher than that of the blaNDM plasmids. In conclusion, two ST11 K. pneumoniae isolates that were part of a hospital outbreak co-harbored blaKPC-2 and blaNDM-1. The blaKPC-harboring IncN plasmid has been circulating in this hospital since at least 2015, and its high copy number might have contributed to the conjugative transfer of this particular plasmid to an E. coli host. The observation that the blaKPC-containing plasmid had a lower copy number in this E. coli strain may explain why this plasmid did not confer phenotypic resistance against meropenem and imipenem.
Antibiotic resistance induced by β-lactamase is posing a significant problem to the pharmaceutical industry. For the last 30 years, only a few inhibitors of β-lactamase were released in the market. The first-generation β-lactamase inhibitors include sulbactam, tazobactam, and clavulanic acid which are derivatives of β-lactams. They mainly function by serine β-lactamases (SBL) inactivation. The next generation of inhibitors of β-lactamase (such as vaborbactam and avibactam) are non-β-lactam derivatives with a broad inhibition range (including KPC, a major class A carbapenemase). Current inhibitors, on the other hand, are resistant to all clinically significant class B β-lactamases and certain class D β-lactamases. This chapter gives information on current research activities aimed at discovering and developing new β-lactamase inhibitors, as well as a summary of recent β lactam/lactamase inhibitor combinations approved by FDA.Keywordsβ-LactamsInhibitorsMultiresistant bacteriaCombination therapy
Despite the availability of various promising antibiotics, bacterial infections still impose a prominent issue of morbidity and mortality. Due to changing environment and widespread misuse of antibiotics, multiple drug- resistance (MDR) strains of bacteria evolved rapidly, intensifying the threat to humankind and environment. Excessive use and diminished potency of current antibiotics against these strains led the foundation; for development of new drug delivery and targeting approaches. Metallic nanoparticles (NPs) provide novel platform to fight against MDR strains. These nano beacons have an intrinsic antibacterial activity or may act as an innovative tool for transporting multiple drugs with augmented biocompatibility. Antibacterial efficiency may be enhanced; by modifying or conjugating surface topology. Intensified NP structure shows effective potency than unmodified ones. This review encompasses how antibacterial activity of NPs offers a novel approach in reducing threats due to MDR bacteria and how their structural changes can affect its antimicrobial activity against MDR.
Increasing carbapenem resistance in Enterobacterales poses a threat to public health. In recent decades, this increase in carbapenem resistance has been caused by the global dissemination of carbapenemase-producing Enterobacterales (CPE). Carbapenemases constitute a class of β-lactamases that are divided into classes A, B, and D based on their molecular structures. Although certain traditionally used antibiotics, such as amikacin, polymyxins, tigecycline, and fosfomycin, may remain effective against some CPEs, their clinical use is limited owing to adverse effects, including renal toxicity, tissue penetration, or requirement for combinatorial treatment. Recently, several novel agents have been approved for clinical use, such as ceftazidime-avibactam, ceftolozane-tazobactam, cefepime-zidebactam, cefiderocol, eravacycline, omadacycline, meropenem-vaborbactam, imipenem-cilastatin-relebactam, and plazomicin. However, the spectrum of antimicrobial activities and efficacies of novel agents vary depending on the mechanisms associated with carbapenem resistance in Enterobacterales. Therefore, it is of utmost importance to enable the accurate and rapid diagnosis of CPE infection, including the determination of their antimicrobial resistance mechanisms. Here, recent advances in the methods for the identification of CPE have been reviewed, including phenotypic methods (carbapenemase inactivation methods), biochemical methods (Carbapenemase Nordmann-Poirel (Carba NP) test and modified Carba NP test), immunochromatographic methods, proteomic methods (matrix-assisted laser desorption/ionization time-of-flight mass spectrometry), and molecular-based methods (nucleic acid amplification technologies, hybridization techniques (microarray), and whole-genome sequencing). Both precise diagnosis and adequate treatment are important to combat the emerging CPE crisis.
Antibiotic-resistant bacteria are considered one of the major global threats to human and animal health. The most harmful of the resistant bacteria are β-lactamases producing Gram-negative species (β-lactamases). β-lactamases constitute a paradigm shift in the evolution of antibiotic resistance. Therefore, it is imperative to present a comprehensive review of the mechanisms responsible for developing antimicrobial resistance. Resistance due to β-lactamases develops through a variety of mechanisms, and the number of resistant genes is involved that can be transferred between bacteria, mostly via plasmids. Over time, these new molecular-based resistance mechanisms have been progressively disclosed. The present review article provides information on the recent findings regarding the molecular mechanisms of resistance to β-lactams in Gram-negative bacteria, including CTX-M-type ESBLs with methylase activity, plasmids harbouring phages with β-lactam resistance genes, the co-presence of β-lactam resistant genes of unique combinations and the presence of β-lactam and non-β-lactam antibiotic-resistant genes in the same bacteria. By keeping in view, the molecular ways of resistance development, multifactorial and coordinated measures may be taken to counter the challenge of rapidly increasing β-lactam resistance.
New Delhi, an enzyme belonging to the Metallo-beta-lactamases and Carbapenemases group, is most commonly found in Klebsiella pneumoniae and Escherichia coli. It determines these bacteria resistance to the majority of known antibiotics. NDM-1 was discovered in 2008 in a man treated in New Delhi for E. coli infection. Since the first appearance, 17 subtypes of this enzyme have been discovered. Its occurrence has been reported in Europe (Great Britain, France, Belgium - where even a national alert has been issued) as well as in the United States and in Africa. Most cases of New Delhi enzyme bacterial infections are reported in India or in people who have traveled to this country. There is no treatment method described so far. Therapy is based on antibiotic susceptibility test results. Colistin shows the highest effectiveness against NDM. There are also tests suggesting that Isomargololone and Nimbolide may be effective in most cases of NDM infection.
The development of pathogenic microbial resistance toward antibiotics has become a global clinical concern. New Delhi metallo-β-lactmase-1 (NDM-1) and its variants have recently drawn immense attention for its biological ability to catalyze the hydrolysis of almost all of β-lactam antibiotics including the Carbapenems which are generally considered as the last-resort antibiotics. Also, the horizontal gene transfer is expediting the rapid spread of NDM-1 in bacteria. In the wake of this serious antibiotic resistance problem it becomes imperative to find inhibitors which can render the present antibiotics functional and useful. In the present study, we have used Molecular docking and Molecular Dynamics (MD) simulation approach to find out suitable inhibitors against NDM-1 from an array of different natural compounds. We have screened unique natural compounds from ZINC database and also a set of standard antibiotics and inhibitors. Based upon the highest binding affinity demonstrated by docking with NDM-1, the best binding antibiotic Meropenem and the top five natural compounds, viz., Withaferin A, Beta-Sitosterol, Aristolochic acid, Diosgenin and Guggulsterone E were selected and subjected to MD simulations study. The docked NDM-1 complex with withaferin A, beta-sitosterol and diosgenin were found to be more stable as compared to the one with meropenem throughout the MD simulation process with the relative RMSD and RMSF in acceptable range. In conclusion, these compounds can be readily tested in vitro and in vivo to fully establish and confirm their inhibition potentiality and can also serve as lead molecules for the development of future functional inhibitors.
Communicated by Ramaswamy H. Sarma
Cancer and autoimmune diseases are the two devastating conditions that together constitute a leading health problem worldwide. The rising burden of these disorders in the developing world demands a multifaceted approach to address the challenges it poses. Understanding the root causes and specific molecular mechanisms by which the progression of the diseases takes place is need of the hour. A strong inflammatory background and common developmental pathways, such as activation of immune cells, proliferation, increased cell survival and migration which are controlled by growth factors and inflammatory cytokines have been considered as the critical culprits in the progression and complications of these disorders. Enzymes are the potential immune modulators which regulate various inflammatory events and can break the circulating immune complexes via macrophages production. In the current manuscript, we have uncovered the possible role of proteolytic enzymes in the pathogenesis and progression of cancer and autoimmune diseases. In the light of the available scientific literature, we advocate in-depth comprehensive studies which will shed light towards the role of proteolytic enzymes in the modulation of inflammatory responses in cancer and autoimmune diseases together.
Antibiotic resistance caused by β-lactamase production continues to present a growing challenge to the efficacy of β-lactams and their role as the most important class of clinically used antibiotics. In response to this threat however, only a handful of β-lactamase inhibitors have been introduced to the market over the past thirty years. The first-generation β-lactamase inhibitors (clavulanic acid, sulbactam and tazobactam) are all β-lactam derivatives and work primarily by inactivating class A and some class C serine β-lactamases. The newer generations of β-lactamase inhibitors including avibactam and vaborbactam are based on non-β-lactam structures and their spectrum of inhibition is extended to KPC as an important class A carbapenemase. Despite these advances several class D and virtually all important class B β-lactamases are resistant to existing inhibitors. The present review provides an overview of recent FDA-approved β-lactam/β-lactamase inhibitor combinations as well as an update on research efforts aimed at the discovery and development of novel β-lactamase inhibitors.
Beta-lactamases are the key enzymes involved in resistance to beta-lactam antibiotics in pathogenic bacteria causing infectious diseases. The search for new inhibitors and the study of the resistance mechanisms require the production of chromogenic substrates for beta-lactamases. A novel cephalosporin derivative with an epoxy functional group named CMPD1 is synthesized. It is shown to be a substrate for TEM type beta-lactamases, which is hydrolyzed to form a colored product. The hydrolysis product has an optical absorption maximum at 450 nm. The difference in the absorption maxima of the substrate and the product is 95 nm, and, therefore, CMPD1 exceeds the previously described substrates, according to this parameter. It has been found that the CMPD1 compound is hydrolyzed only by the TEM type beta-lactamases that lack mutations in the active site. This can be used to study the mechanisms of the catalytic effect of beta-lactamases.
Neonates present particular problems in prescribing compared with older children and adults. Oral absorption is variable making oral therapy unreliable in general. The extracellular fluid volume is proportionally higher in newborns, so antibiotics like aminoglycosides which are distributed in the extracellular space achieve lower peak levels than older children for a comparable per kilogram dose and persist longer. Drug toxicity is a greater problem in neonates. This chapter talks about antimicrobials for neonates. Penicillin is cheap and extremely safe, and remains the antibiotic of choice for susceptible organisms. Second-generation cephalosporins (including cefuroxime, cefoxitin, cefaclor) have improved activity against Gram-negative bacilli compared with first-generation cephalosporins. The chapter also discusses other antibiotics such as aztreonam, carbapenems, glycopeptides, linezolid, daptomycin, macrolides, quinolones, metronidazole, rifamycin, antifungals, and chloramphenicol.
Objective: To investigate the molecular epidemiological significance of isolating a New Delhi metallo-β-lactamase-1 (NDM-1) producing Klebsiella pneumoniae (K. pneumoniae) strain. Methods: The strain was a carbapenems resistant K. pneumoniae strain isolated from clinical samples. VITEK-2 Compact instrument was used for identification and antibiotic susceptibility test. Expressions of NDM-1 genes and carbapenemases genes were detected by the PCR. The transfer plasmid conjugation experiment and multilocus sequence typing (MLST) were performed. MLST data of NDM-1 producing K. pneumoniae from other areas was collected from PubMed and analyzed by eBURST V3 software and Tree drawing software. Results: The isolated strain was highly resistant to many antibiotics including carbpenems and carried the NDM-1 gene. Plasmids that contained the NDM-1 gene were successfully transferred to recipient bacteria by conjugation and the MLST of K. pneumoniae strain was ST571. The MLST data of 283 NDM-1 producing K. pneumoniae strains from 28 countries were collected, including 42 ST strains. The major epidemic strain was CC258 strain (clone complex). Conclusion: The ST571 NDM-1 producing K. pneumoniae strain is isolated in China for the first time. The drug resistant gene may be transmitted by plasmids. The molecular typing of NDM-1 producing K. pneumoniae is diverse. CC258 strain is the most epidemic strain. The isolated strain is genetically far from cloned CC258 strain. ©, 2015, Editorial Department of Journal of Shanghai Second Medical University. All right reserved.
Gram-negative carbapenem-resistant bacteria, in particular those producing New Delhi Metallo-beta-lactamase-1 (NDM-1), are a major global health problem. To inform the scientific and medical community in real time about worldwide dissemination of isolates of NDM-1-producing bacteria, we used the PubMed database to review all available publications from the first description in 2009 up to 31 December 2012, and created a regularly updated worldwide dissemination map using a web-based mapping application. We retrieved 33 reviews, and 136 case reports describing 950 isolates of NDM-1-producing bacteria. Klebsiella pneumoniae (n= 359) and Escherichia coli (n=268) were the most commonly reported bacteria producing NDM-1 enzyme. Several case reports of infections due to imported NDM-1 producing bacteria have been reported in a number of countries, including the United Kingdom, Italy, and Oman. In most cases (132/153, 86.3%), patients had connections with the Indian subcontinent or Balkan countries. Those infected were originally from these areas, had either spent time and/or been hospitalised there, or were potentially linked to other patients who had been hospitalised in these regions. By using Google Maps, we were able to trace spread of NDM-1-producing bacteria. We strongly encourage epidemiologists to use these types of interactive tools for surveillance purposes and use the information to prevent the spread and outbreaks of such bacteria.
This article reviews the global crisis of resistant gram-negative bacilli in the intensive care unit. The authors discuss drugs used for treating these infections and the different strategies used to maximize the effect of antimicrobials.
Bacteria, beside other microorganisms are mainly responsible for human sufferings beside their beneficial effects. After discovery of Penicillin bacterial diseases were controlled to a much extent. The name 'antibiotic' makes us feel that we, humans are superior at least from microorganisms. Serious infections caused by bacteria that have become resistant to commonly used antibiotics have become a major global healthcare problem in the 21st century. Resistance to antibiotics shows that they can fight back and challenge our knowledge and intellect. Discovery of New Delhi metallo-1 make us feel that this is the result of our own ignorance. Indiscriminate, irrational and illogical use of antibiotics is helping bacteria to fight against us. What objections are being raised at the Govt. level, and how research community defends us, keeping that apart, the question is to realize and resolve the threat rather than to overlook it. Our outlook need to be changed and health policies and guidelines need to be reevaluated and overhauled timely.
New Delhi metallo-beta-lactamase (NDM-1) is an enzyme that makes bacteria resistant to a broad range of beta-lactam antibiotic drugs. This is because it can inactivate most beta-lactam antibiotic drugs by hydrolyzing them. For in-depth understanding of the hydrolysis mechanism, the three-dimensional structure of NDM-1 was developed. With such a structural frame, two enzyme-ligand complexes were derived by respectively docking Imipenem and Meropenem (two typical beta-lactam antibiotic drugs) to the NDM-1 receptor. It was revealed from the NDM-1/Imipenem complex that the antibiotic drug was hydrolyzed while sitting in a binding pocket of NDM-1 formed by nine residues. And for the case of NDM-1/Meropenem complex, the antibiotic drug was hydrolyzed in a binding pocket formed by twelve residues. All these constituent residues of the two binding pockets were explicitly defined and graphically labeled. It is anticipated that the findings reported here may provide useful insights for developing new antibiotic drugs to overcome the resistance problem.
This work reports, for the first time, the presence of New Delhi metallo-β-lactamase 1 (NDM-1) in Pseudomonas aeruginosa. Moreover, this is the first report of the NDM-1 presence in the Balkan region. Cosmid gene libraries of carbapenem-nonsusceptible
Pseudomonas aeruginosa clinical isolates MMA83 and MMA533 were screened for the presence of metallo-β-lactamases. Accordingly, both MMA83 and MMA533
carried the blaNDM-1 gene. Pulsed-field gel electrophoresis (PFGE) analysis indicated that strains MMA83 and MMA533 belonged to different clonal
groups. Five additional isolates from different patients clonally related to either MMA83 or MMA533 were found to be NDM-1
positive.
New Delhi metallo-β-lactamase-1 (NDM-1) is a recently identified metallo-β-lactamase that confers resistance to carbapenems and all other β-lactam antibiotics, with the exception of aztreonam. NDM-1 is also associated with resistance to many other classes of antibiotics. The enzyme was first identified in organisms isolated from a patient in Sweden who had previously received medical treatment in India, but it is now recognized as endemic throughout India and Pakistan and has spread worldwide. The gene encoding NDM-1 has been found predominantly in Escherichia coli and Klebsiella pneumoniae. We describe the isolation NDM-1-producing organisms from two patients in Toronto, Ontario. To the best of our knowledge, this is the first report of an organism producing NDM-1 that was locally acquired in Canada. We also discuss the evidence that NDM-1 can affect bacterial species other than E. coli and K. pneumoniae, the limited options for treatment and the difficulty laboratories face in detecting organisms that produce NDM-1.
An NDM-1 carbapenemase-producing Escherichia coli isolate of sequence type 131 (ST131) that belonged to phylogenetic group B2 was obtained from a patient with a urinary tract
infection who returned to the United States after a recent hospitalization while visiting India. NDM-1-producing E. coli ST131 had significantly more virulence factors than NDM-1-producing E. coli ST101, previously isolated from a patient in Canada. The presence of NDM β-lactamases in a very successful and virulent E. coli sequence type is of concern.
Five multidrug-resistant nonclonally related Enterobacteriaceae isolates were recovered in Belgium in 2010 from three patients who had been hospitalized in Pakistan, Montenegro, and Serbia/Kosovo.
New Delhi metallo-β-lactamase (NDM-1) was detected in each of the isolates in addition to several extended-spectrum β-lactamases
(CTX-M-15, SHV-12), plasmidic cephalosporinases (CMY-16, CMY-58), rRNA methylases (ArmA, RmtB), and Qnr genes (qnrA6, qnrB1, qnrB2). One patient died from uncontrolled sepsis, while the two others recovered. No secondary cases occurred in any of the hospitals.
To analyse the mechanisms responsible for carbapenem resistance in one Acinetobacter baumannii isolate recovered from a patient transferred to Germany from an Egyptian hospital.
PCR and sequencing were used to search for β-lactamase and 16S RNA methylase genes. Multilocus sequence typing was used to determine the sequence type (ST) of the isolate.
Sequencing of the PCR product obtained using primers for bla(NDM-1) revealed a variant of NDM-1 that had a C to G substitution at position 82 resulting in an amino acid substitution of proline to alanine at position 28. This variant was designated NDM-2. Genes encoding extended-spectrum β-lactamases or 16S RNA methylase were not detected. The strain lacked detectable plasmids and bla(NDM-2) was not transferred by conjugation. MLST showed that the isolate belonged to a new ST, ST103.
This work further underlines the spread of NDM carbapenemases in A. baumannii, and the spread of the corresponding gene in the Middle East. It also describes the first variant of NDM-1.
The NDM-1 gene, first identified in Sweden in 2008 in Klebsiella pneumoniae from a patient hospitalized in New Delhi, encodes a metallo-β-lactamase that inactivates all β-lactams except aztreonam. This bla(NDM-1) gene has been identified in hospital-acquired bacterial species, such as K. pneumoniae, but also in the typical community-acquired species, Escherichia coli. This gene has been identified in strains that possess other resistance mechanisms contributing to their multidrug resistance patterns. It has been recently extensively reported from the UK, India and Pakistan and, albeit to a lesser extent, from a number of other countries worldwide. In most of the cases a link with the Indian subcontinent has also been established. To stem the onslaught of NDM producers, early identification of cases of NDM-related infections and prevention of their spread by implementing screening, hygiene measures and the isolation of carriers is needed.
The Check-MDR CT102 microarray, aimed at identifying bacteria producing extended-spectrum β-lactamase (ESBL) (SHV, TEM, and
CTX-M) and carbapenemase (KPC, OXA-48, VIM, IMP, and NDM-1), was evaluated on a total of 144 Gram-negative strains expressing
various β-lactamases. The sensitivity and specificity were 100% for most tested genes, suggesting that this assay allows accurate
identification of common ESBL and carbapenemase producers from bacterial cultures.
To the Editor: The New Delhi metallo-beta-lactamase (NDM-1) was first characterized in 2009 from Klebsiella pneumoniae and Escherichia coli isolated from a patient in Sweden who had received medical care in New Delhi, India (1). Further studies have shown broad dissemination of this beta-lactamase gene (blaNDM-1) in India, Pakistan, Bangladesh, and the United Kingdom (2). Additional isolates have been detected in other countries, and many of the patients with NDM-1-producing Enterobacteriaceae reported receiving medical care in the Indian subcontinent (1-7). We describe detection and characterization of an NDM-1-producing K. pneumoniae isolated in Ontario, Canada.
The carbapenemase NDM-1 has been initially identified in Escherichia and Klebsiella pneumoniae in Sweden from a patient transferred from India (10)....
Multidrug-resistant Klebsiella pneumoniae and Escherichia coli isolates harboring New Delhi metallo-β-lactamase (NDM-1) were isolated from a patient who had returned to Canada from India. The NDM-1 gene was found on closely related incompatibility group A/C type plasmids. The occurrence of NDM-1 in North America is a major public health concern.
Enterobacterial isolates expressing the carbapenemase NDM-1 are emerging worldwide. Twenty-seven NDM-1-positive isolates of
worldwide origin were included in this study to identify these strains as not only pathogens but also colonizers of normal
flora for infection control screening. Although susceptibility to carbapenems varied, a combined test (IMP/IMP + EDTA), the
Etest MBL, and automated susceptibility testing by Vitek2 (bioMérieux) identified those NDM-1 producers as verified by PCR
using specific primers. Screening for carriers of NDM-1 producers may be based on media such as the ChromID ESBL culture medium
routinely used to screen for extended-spectrum β-lactamase producers, which gives excellent detection levels with low limits
of detection ranging from 8 × 100 to 5 × 102 CFU/ml. The CHROMagar KPC culture medium had higher limits of detection (1 × 101 to 5 × 105 CFU/ml) and may be proposed for the follow-up of outbreaks of infections with NDM-1 producers. Colonies growing on these
screening media can be verified as NDM-1 producers with molecular methods as described herein.
This one-year study describes isolation of 6 carbapenem-resistant Acinetobacter baumannii strains from 920 urine samples from urinary tract infection patients attending an indian hospital. A search for bla(CTX-M), bla(TEM), armA, rmtA, rmtB and integrons was performed. four strains were identified as extended-spectrum-β-lactamase (ESBL)-producers. Two bla(CTX-M-15 )and 2bla(TEM-150 )and 3 Class 1 integrons were amplified. Ceftazidime and cefotaxime resistance markers were found to be located on the plasmid DNA of the clonally related bla (CTX-M-15)-positive strains and were transmissible through conjugation. Ramachandran Z-score for modeled-CTX-M was found to be -1.277. The study suggests that in regions having known prevalence of bacteria simultaneously resistant to carbapenems and advanced generation cephalosporins, the drugs of choice for empiric treatment could be amikacin and ampicillin/sulbactam. Furthermore, we recommend extensive use of bioinformatics tools to understand structures of CTX-M-variants as these are emerging at a fast pace and it is painstaking to crystallize each variant.
To analyse the mechanisms responsible for multidrug resistance in two carbapenem-resistant Klebsiella pneumoniae isolates recovered from patients hospitalized in Oman.
PCR and sequencing were used to search for β-lactamase and 16S RNA methylase genes. Multilocus sequence typing was used to determine the sequence type (ST) of each isolate. Clonal relationships were evaluated by PFGE.
Both isolates carried the bla(NDM-1) carbapenemase gene. Isolate 601 was recovered from a patient who was transferred from India, whereas isolate 419 was from an Omani patient who had not travelled abroad. The two isolates were clonally unrelated, and belonged to ST14 (isolate 601) and ST340 (isolate 419). In addition to NDM-1, the ST14 isolate expressed β-lactamases CTX-M-15, SHV-28, OXA-1, OXA-9 and TEM-1, and the aminoglycoside resistance methylase ArmA. The ST340 isolate expressed β-lactamases SHV-11, OXA-1 and ArmA. In both isolates, the bla(NDM-1) gene was located on plasmids that were of similar size (170 kb), but of different incompatibility groups.
This is the first description of NDM-1 producers in the Arabian peninsula and in the Middle East.
Combinations of NXL104 with ceftazidime and aztreonam were tested against carbapenem-resistant members of the Enterobacteriaceae. Ceftazidime-NXL104 was active against strains with the OXA-48 enzyme or with combinations of impermeability and an extended-spectrum
β-lactamase (ESBL) or AmpC enzyme and also against most Klebsiella spp. with the KPC enzyme, but metallo-β-lactamase producers were resistant. Aztreonam-NXL104 was active against all carbapenemase
producers at 4 and 4 μg/ml, including those with metallo-β-lactamases.
To determine the molecular characterization of extended-spectrum beta-lactamases (ESBL) isolates from a tertiary center in Saudi Arabia using multiplex polymerase chain reaction (PCR) technique and assess their antibiotic susceptibility pattern.
Prospective study conducted at the Saudi Aramco Dhahran Health Center, Dhahran, Saudi Arabia between April-December 2006. Extended-spectrum beta-lactamases phenotype of isolates identified by automated methods was confirmed using E-test. Multiplex PCR for the detection of blaTEM, blaSHV and blaCTX-M was performed. Susceptibility to a panel of antibiotics was determined.
One hundred isolates (Escherichia coli [E.coli] n=84; Klebsiella pneumoniae [K. pneumoniae] n=16) were studied and 71% harbored the blaCTX-M gene. For E.coli isolates 43 (51%) harbored CTX-M+TEM combination and 21 (25%) had CTX-M alone. In contrast, only one K. pneumoniae isolate (6.2%) harbored the CTX-M+TEM combination and 3 (18.8%) isolates had CTX-M only. One E.coli and 7 K. pneumoniae isolates were blaSHV positive. The blaCTX-M gene was found predominantly in urinary isolates (n=63/71; 88.7%). The presence of blaCTX-M was significantly higher in isolates from outpatients compared to inpatient (p<0.05). Sensitivity to imipenem was 100% and 78% to nitrofurantoin. Resistance to amoxicillin-sulbactam was significantly higher in blaCTX-M positive isolates (p<0.05).
The findings indicate a high-level of blaCTX-M positive ESBL isolates circulating in our setting with the dissemination of these in the community. The trend of multidrug resistance profile associated with carriage of blaCTX-M gene is cause for concern.
Gram-negative Enterobacteriaceae with resistance to carbapenem conferred by New Delhi metallo-beta-lactamase 1 (NDM-1) are potentially a major global health problem. We investigated the prevalence of NDM-1, in multidrug-resistant Enterobacteriaceae in India, Pakistan, and the UK.
Enterobacteriaceae isolates were studied from two major centres in India--Chennai (south India), Haryana (north India)--and those referred to the UK's national reference laboratory. Antibiotic susceptibilities were assessed, and the presence of the carbapenem resistance gene bla(NDM-1) was established by PCR. Isolates were typed by pulsed-field gel electrophoresis of XbaI-restricted genomic DNA. Plasmids were analysed by S1 nuclease digestion and PCR typing. Case data for UK patients were reviewed for evidence of travel and recent admission to hospitals in India or Pakistan.
We identified 44 isolates with NDM-1 in Chennai, 26 in Haryana, 37 in the UK, and 73 in other sites in India and Pakistan. NDM-1 was mostly found among Escherichia coli (36) and Klebsiella pneumoniae (111), which were highly resistant to all antibiotics except to tigecycline and colistin. K pneumoniae isolates from Haryana were clonal but NDM-1 producers from the UK and Chennai were clonally diverse. Most isolates carried the NDM-1 gene on plasmids: those from UK and Chennai were readily transferable whereas those from Haryana were not conjugative. Many of the UK NDM-1 positive patients had travelled to India or Pakistan within the past year, or had links with these countries.
The potential of NDM-1 to be a worldwide public health problem is great, and co-ordinated international surveillance is needed.
Extended-spectrum beta-lactamases (ESBLs) are bacterial enzymes that confer resistance to advanced generation cephalosporins and can lead to therapeutic failures. There has been no analysis of factors associated with the risk of acquisition of ESBLs in neonates in an intensive care unit from northern India. The CTX-M ESBL enzymes impart resistance against advanced generation cephalosporins (e.g. cefotaxime) and CTX-M variants have become the most prevalent ESBLs worldwide. The CTX-M-15 enzyme in particular is increasingly being reported from Escherichia coli isolates from northern India together with TEM-1. Moreover, E. coli is the most common cause of neonatal sepsis. Accordingly, this study aimed to: (i) characterize the mode of transmission of bla(CTX-M) and bla(TEM) among ESBL-producing E. coli strains isolated from patients admitted to a neonatal intensive care unit (NICU), and (ii) identify factors associated with the acquisition of the said strains in male and female neonates. A total of 97 ESBL-producers was identified among 266 E. coli strains isolated from 238 neonates. The isolates were screened for bla(CTX-M), bla(TEM), armA, rmtA and rmtB, the last three genes being responsible for aminoglycoside resistance. PCR amplified bla(CTX-M) genes were cloned and sequenced. Five bla(CTX-M-15), two rmtB, two bla(TEM-1) and thirteen class1 integrons were detected. All the bla(CTX-M-15) positive isolates, except one, were clonally related. Both univariate and multivariate analyses of factors for the acquisition of the said strains were performed with respect to the sex of the neonates. 'Length of stay in the NICU' was found to be the single independent factor associated with ESBL acquisition. In conclusion, our data suggest that male neonates who are colonized or infected by ESBL-producing E. coli have a longer stay in the NICU compared to their female counterparts. This prolonged stay may be due to male neonates becoming colonized/infected earlier than their female counterparts. Plasmid-mediated-conjugal transfer was found to be the mechanism of transfer of the bla(CTX-M-15) resistance marker in the described setting.
Extended-spectrum-β-lactamases (ESBLs) are enzymes produced by bacteria which impart resistance againstadvanced-generation-cephalosporins. CTX-M enzymes have become the most prevalent ESBLs. The amino acidresidues through which 2009 CTX-M-variants interact with drugs and inhibitors is not reported. Homology models forCTX-M-15 (This study), CTX-M-53, CTX-M-71, CTX-M-82 and CTX-M-89 were prepared. Ramachandran-Z-scoresfor models were found to be -0.449, 0.006, -0.103, -0.007 and 0.092, respectively. These models were docked withtarget drugs (cefotaxime, ceftazidime, cefepime) and inhibitors (clavulanate, sulbactam, tazobactam). The blaCTX-M-15marker was PCR-amplified from plasmid DNA of clinical Escherichia coli isolate. Minimum inhibitory concentrations(MICs) for drugs were tested by the microbroth-dilution-method. E. coli C600 cells (harboring cloned blaCTX-M-15) werefound positive for ESBL-production by the double-disk-synergy test. The blaCTX-M-15 marker was found transmissiblethrough conjugation. Discovery Studio analysis of the docked structures revealed that irrespective of the CTX-M-type,ceftazidime interacted with the residues A226, G227, L228, P229, A/T230, S231, W232, R285, T288, D289, G290 andL/Y291. Moreover, sulbactam was found to bind most efficiently to the studied enzymes on the basis of interactionenergies. The study identifies amino acid residues crucial to ‘CTX-M-drug’ and ‘CTX-M-inhibitor’ interactions whichmight be useful in the ongoing search for a versatile CTX-M-inhibitor.
The study aimed at (i) characterizing the mode of transmission of bla(CTX-M) and bla(TEM-1) among extended-spectrum-beta-lactamase (ESBL)-producing Escherichia coli strains isolated from infected diabetic foot ulcers, and (ii) identifying the risk factors for "sex-associated multidrug resistant Gram-negative bacterial (MDRGNB)-infection status" of the ulcers.
Seventy-seven diabetic patients having clinically infected foot ulcers were studied in a consecutive series. The E. coli strains isolated from the ulcers were screened for bla(CTX-M), bla(TEM-1), armA, rmtA and rmtB during the 2-year study-period. PCR amplified bla(CTX-M) genes were cloned and sequenced. Enterobacterial repetitive intergenic consensus (ERIC)-PCR was used for the analysis of genetic relatedness of the ESBL-producers. Risk factors for "sex-associated MDRGNB-infection status" of ulcers were assessed. Modeling was performed using Swiss-Model-Server and verified by Procheck and verify3D programmes. Discovery Studio2.0 (Accelrys) was used to prepare Ramachandran plots. Z-scores were calculated using 'WHAT IF'-package. Docking of cefotaxime with modeled CTX-M-15 enzyme was performed using Hex5.1.
Among 51 E. coli isolates, 14 (27.5%) ESBL-producers were identified. Only 7 Class1 integrons, 2 bla(CTX-M-15), and 1 bla(TEM-1) were detected. Ceftazidime and cefotaxime resistance markers were present on the plasmidic DNA of both the bla(CTX-M-15) positive strains and were transmissible through conjugation. The residues Asn132, Glu166, Pro167, Val172, Lys234 and Thr235 of CTX-M-15 were found to make important contacts with cefotaxime in the docked-complex. Multivariate analysis proved 'Glycemic control at discharge' as the single independent risk factor.
Male diabetic patients with MDRGNB-infected foot ulcers have poor glycemic control and hence they might have higher mortality rates compared to their female counterparts. Plasmid-mediated conjugal transfer, albeit at a low frequency might be the possible mechanism of transfer of bla(CTX-M-15) resistance marker in the present setting. Since the docking results proved that the amino acid residues Asn132, Glu166, Pro167, Val172, Lys234 and Thr235 of CTX-M-15 (enzyme) make important contacts with cefotaxime (drug) in the 'enzyme-drug complex', researchers are expected to duly utilize this information for designing more potent and versatile CTX-M-inhibitors.
Doripenem is a new 1-beta-methyl carbapenem with broad-spectrum activity against clinically important pathogens. Its activity matches imipenem or ertapenem against Gram-positive bacteria and meropenem against Gram-negative bacteria. It may offer slightly more activity than meropenem against selected pathogens. It does not require the addition of cilastatin. Doripenem is stable to hydrolysis by most of the beta-lactamases, excluding carbapenem-hydrolyzing beta-lactamases. We performed dockings of imipenem, meropenem, ertapenem and doripenem with imipenem-hydrolyzing beta-lactamase, Sme1, separately. Energy calculations revealed that the complex involving doripenem was much less stable. Hence doripenem resists attack by carbapenem-hydrolyzing beta-lactamases at least to some extent. Empiric therapy with doripenem may be useful in hospital settings where multidrug resistance has emerged. However, the proper place for this drug in current antibiotic prescribing practices needs to be determined.
A Swedish patient of Indian origin traveled to New Delhi, India, and acquired a urinary tract infection caused by a carbapenem-resistant
Klebsiella pneumoniae strain that typed to the sequence type 14 complex. The isolate, Klebsiella pneumoniae 05-506, was shown to possess a metallo-β-lactamase (MBL) but was negative for previously known MBL genes. Gene libraries
and amplification of class 1 integrons revealed three resistance-conferring regions; the first contained blaCMY-4 flanked by ISEcP1 and blc. The second region of 4.8 kb contained a complex class 1 integron with the gene cassettes arr-2, a new erythromycin esterase gene; ereC; aadA1; and cmlA7. An intact ISCR1 element was shown to be downstream from the qac/sul genes. The third region consisted of a new MBL gene, designated blaNDM-1, flanked on one side by K. pneumoniae DNA and a truncated IS26 element on its other side. The last two regions lie adjacent to one another, and all three regions are found on a 180-kb
region that is easily transferable to recipient strains and that confers resistance to all antibiotics except fluoroquinolones
and colistin. NDM-1 shares very little identity with other MBLs, with the most similar MBLs being VIM-1/VIM-2, with which
it has only 32.4% identity. As well as possessing unique residues near the active site, NDM-1 also has an additional insert
between positions 162 and 166 not present in other MBLs. NDM-1 has a molecular mass of 28 kDa, is monomeric, and can hydrolyze
all β-lactams except aztreonam. Compared to VIM-2, NDM-1 displays tighter binding to most cephalosporins, in particular, cefuroxime,
cefotaxime, and cephalothin (cefalotin), and also to the penicillins. NDM-1 does not bind to the carbapenems as tightly as
IMP-1 or VIM-2 and turns over the carbapenems at a rate similar to that of VIM-2. In addition to K. pneumoniae 05-506, blaNDM-1 was found on a 140-kb plasmid in an Escherichia coli strain isolated from the patient's feces, inferring the possibility of in vivo conjugation. The broad resistance carried
on these plasmids is a further worrying development for India, which already has high levels of antibiotic resistance.
Tigecycline is the first Food and Drug Administration (FDA) approved glycylcycline antibiotic. It has shown remarkable in vitro activity against a wide variety of gram-positive, gram-negative and anaerobic bacteria including many multidrug resistant (MDR) strains. However, it has minimal activity against Pseudomonas aeruginosa and Proteus spp. To date, little resistance to tigecycline has been reported. Clinical trials studying complicated skin and skin-structure infections (cSSSIs) demonstrated that tigecycline has equivalent efficacy and safety compared with the combination of vancomycin and aztreonam. For complicated intra-abdominal infections (cIAIs), tigecycline was found to be as effective as imipenem/cilastatin. Adverse events related to tigecycline therapy, i.e. nausea and vomiting, were tolerable. Currently available data suggest that tigecycline may play an important role in the future as a monotherapy alternative to older broad-spectrum antibiotics, such as advanced generation cephalosporins, carbapenems, fluoroquinolones, piperacillin/tazobactam, and gram-positive directed agents (e.g. daptomycin, linezolid and quinupristin/dalfopristin) for which resistance is being increasingly reported from all parts of the world.
Since 1944, we have come a long way using aminoglycosides as antibiotics. Bacteria also have got them selected with hardier resistance mechanisms. Aminoglycosides are aminocyclitols that kill bacteria by inhibiting protein synthesis as they bind to the 16S rRNA and by disrupting the integrity of bacterial cell membrane. Aminoglycoside resistance mechanisms include: (a) the deactivation of aminoglycosides by N-acetylation, adenylylation or O-phosphorylation, (b) the reduction of the intracellular concentration of aminoglycosides by changes in outer membrane permeability, decreased inner membrane transport, active efflux, and drug trapping, (c) the alteration of the 30S ribosomal subunit target by mutation, and (d) methylation of the aminoglycoside binding site. There is an alarming increase in resistance outbreaks in hospital setting. Our review explores the molecular understanding of aminoglycoside action and resistance with an aim to minimize the spread of resistance.
Antibiotic resistance is a major public health concern, with fears expressed that we shortly will run out of antibiotics. In reality, the picture is more mixed, improving against some pathogens but worsening against others. Against methicillin-resistant Staphylococcus aureus (MRSA)--the highest profile pathogen--the range of treatment options is expanding, with daptomycin, linezolid and tigecycline all launched, and telavancin, ceftobiprole, ceftaroline and dalbavancin anticipated. There is a greater problem with enterococci, especially if, as in endocarditis, bactericidal activity is needed and the isolate has high-level aminoglycoside resistance; nevertheless, daptomycin, telavancin and razupenem all offer cidal potential. Against Enterobacteriaceae, the rapid and disturbing spread of extended-spectrum beta-lactamases, AmpC enzymes and quinolone resistance is forcing increased reliance on carbapenems, with resistance to these slowly accumulating via the spread of metallo-, KPC and OXA-48 beta-lactamases. Future options overcoming some of these mechanisms include various novel beta-lactamase-inhibitor combinations, but none of these overcomes all the carbapenemase types now circulating. Multiresistance that includes carbapenems is much commoner in non-fermenters than in the Enterobacteriaceae, depending mostly on OXA carbapenemases in Acinetobacter baumannii and on combinations of chromosomal mutation in Pseudomonas aeruginosa. No agent in advanced development has much to offer here, though there is interest in modified, less-toxic, polymyxin derivatives and in the siderophore monobactam BAL30072, which has impressive activity against A. baumannii and members of the Burkholderia cepacia complex. A final and surprising problem is Neisseria gonorrhoeae, where each good oral agent has been eroded in turn and where there is now little in reserve behind the oral oxyimino cephalosporins, to which low-level resistance is emerging.
To analyse the mechanisms responsible for decreased susceptibility or resistance to carbapenems in several enterobacterial isolates recovered in 2009-10 in Geneva University Hospitals, Switzerland.
PCR and sequencing were used to identify β-lactamases, 16S RNA methylases and plasmid-mediated quinolone resistance genes. The transferable properties of the plasmids were analysed, as well as their plasmid type. The strains were typed by multilocus sequence typing.
Three patients were found to be positive for NDM-1-producing enterobacterial isolates (one with Escherichia coli and Klebsiella pneumoniae, one with K. pneumoniae only and one with Proteus mirabilis), where NDM-1 stands for New Delhi metallo-β-lactamase-1. The bla(NDM-1) carbapenemase gene was detected in all isolates in addition to genes encoding narrow-spectrum β-lactamases (TEM-1, SHV-11, OXA-1, OXA-9 and OXA-10), extended-spectrum β-lactamases (CTX-M-15, CMY-16 and CMY-30), ArmA and quinolone resistance determinants (Qnr). The bla(NDM-1) gene was located on conjugative IncA/C- or IncF-type plasmids. Upstream of the bla(NDM-1) gene, part of ISAba125, previously identified in NDM-1-negative Acinetobacter baumannii, was found. Downstream of the bla(NDM-1) gene, variable sequences were found.
This work constitutes the first identification of NDM-1 producers in Switzerland. Interestingly, patients from whom these NDM-1-producing isolates were recovered had a link with the Indian subcontinent or the Balkans.
Metallo-β-lactamases (MBLs) hydrolyze most β-lactam antibiotics, and bacteria containing this kind of enzyme pose a serious threat to the public health. The newly identified New Delhi MBL (NDM-1) is a new member of this family that shows tight binding to penicillin and cephalosporins. The rapid dissemination of NDM-1 in clinically relevant bacteria has become a global concern. However, no clinically useful inhibitors against MBLs exist, partly due to the lack of knowledge about the catalysis mechanism of this kind of enzyme. Here we report the crystal structure of this novel enzyme in complex with a hydrolyzed ampicillin at its active site at 1.3-Å resolution. Structural comparison with other MBLs revealed a new hydrolysis mechanism applicable to all three subclasses of MBLs, which might help the design of mechanism based inhibitors.
In this study, we report the development of a rapid real-time polymerase chain reaction (PCR) assay with TaqMan probe to detect the New Delhi metallo-β-lactamase (NDM-1)-encoding gene directly from bacterial isolates. The specificity of the assay was verified in silico as well as with a large panel of 84 clinically relevant bacteria, including the Klebsiella pneumoniae NCTC 13443 NDM-1-positive reference strain. Using this assay retrospectively on a local series of 44 K. pneumoniae isolates from Marseille Hospitals (France), it was possible to detect and identify an NDM-1-producing K. pneumoniae strain isolated from bronchoalveolar lavage in April 2010 from a French patient repatriated from India after a motorbike accident. Standard PCR amplification and sequencing of the entire NDM-1 gene from this isolate was also performed and the amino acid sequence showed 100% homology with the NDM-1 protein from the K. pneumoniae reference strain. We believe that this real-time PCR assay would be a powerful tool that could be added to other molecular detection assays such as detection of KPC- or OXA-encoding genes for rapid screening and/or identification of carbapenem-resistant bacterial isolates from patients returning from the Asian continent that could be implemented in a point-of-care strategy.
Not all patients infected with NDM-1-positive bacteria have a history of hospital admission in India, and extended-spectrum β-lactamases are known to be circulating in the Indian community. We therefore measured the prevalence of the NDM-1 gene in drinking water and seepage samples in New Delhi.
Swabs absorbing about 100 μL of seepage water (ie, water pools in streets or rivulets) and 15 mL samples of public tap water were collected from sites within a 12 km radius of central New Delhi, with each site photographed and documented. Samples were transported to the UK and tested for the presence of the NDM-1 gene, bla(NDM-1), by PCR and DNA probing. As a control group, 100 μL sewage effluent samples were taken from the Cardiff Wastewater Treatment Works, Tremorfa, Wales. Bacteria from all samples were recovered and examined for bla(NDM-1) by PCR and sequencing. We identified NDM-1-positive isolates, undertook susceptibility testing, and, where appropriate, typed the isolates. We undertook Inc typing on bla(NDM-1)-positive plasmids. Transconjugants were created to assess plasmid transfer frequency and its relation to temperature.
From Sept 26 to Oct 10, 2010, 171 seepage samples and 50 tap water samples from New Delhi and 70 sewage effluent samples from Cardiff Wastewater Treatment Works were collected. We detected bla(NDM-1) in two of 50 drinking-water samples and 51 of 171 seepage samples from New Delhi; the gene was not found in any sample from Cardiff. Bacteria with bla(NDM-1) were grown from 12 of 171 seepage samples and two of 50 water samples, and included 11 species in which NDM-1 has not previously been reported, including Shigella boydii and Vibrio cholerae. Carriage by enterobacteria, aeromonads, and V cholera was stable, generally transmissible, and associated with resistance patterns typical for NDM-1; carriage by non-fermenters was unstable in many cases and not associated with typical resistance. 20 strains of bacteria were found in the samples, 12 of which carried bla(NDM-1) on plasmids, which ranged in size from 140 to 400 kb. Isolates of Aeromonas caviae and V cholerae carried bla(NDM-1) on chromosomes. Conjugative transfer was more common at 30°C than at 25°C or 37°C.
The presence of NDM-1 β-lactamase-producing bacteria in environmental samples in New Delhi has important implications for people living in the city who are reliant on public water and sanitation facilities. International surveillance of resistance, incorporating environmental sampling as well as examination of clinical isolates, needs to be established as a priority.
European Union.
