[Show abstract][Hide abstract] ABSTRACT: We investigated the synergism of colistin and imipenem against a multidrug-resistant K. pneumoniae isolate which was recovered from a severe hip infection. PCR and DNA sequencing were used to characterize the outer membrane porin genes and the resistance genes mediating the common β-lactamases and carbapenemases. Synergism was evaluated by time-kill studies. The , , and were detected. Outer membrane porin genes analysis revealed loss of ompK36 and frame-shift mutation of ompK35. The common carbapenemase genes were not found. Time-kill studies demonstrated that a combination of 1x MIC of colistin (2 mg/L) and 1x MIC of imipenem (8 mg/L) was synergistic and bactericidal but with inoculum effect. Bactericidal activity without inoculum effect was observed by concentration of 2x MIC of colistin alone or plus 2x MIC of imipenem. In conclusion, colistin plus imipenem could be an alternative option to treat carbapenem-resistant K. pneumoniae infections.
[Show abstract][Hide abstract] ABSTRACT: Two Klebsiella pneumoniae isolates were simultaneously recovered from blood and urine cultures of the same patient. Both isolates were identical in genomic pulsotype by pulsed-field gel electrophoresis (PFGE). However, the hypermucoviscosity phenotype was confirmed in the blood strain but not the urine strain. A previously unrelated liver abscess K. pneumoniae hypermucoviscous isolate was used as a control. PCR, DNA cloning and sequencing for the plasmid-borne rmpA and rmpA2 genes and the chromosome-borne rmpA gene (c-rmpA) revealed negative c-rmpA with natural frame-shift mutation of rmpA and rmpA2 genes in the urine strain. The blood strain was negative for c-rmpA with rmpA2 mutation but no mutation in rmpA. The control strain was positive for c-rmpA with rmpA2 mutation but no mutation in rmpA and showed the highest virulence in mouse lethality experiments [median lethal dose (LD50) = 50 CFU], which was followed by the blood strain (LD50 = 2.47 × 103 CFU) and the urine strain (LD50 > 107 CFU). The control and blood strains were highly serum resistant, whereas the urine strain was sensitive to serum killing. In conclusion, intrapersonal concurrent mutation of rmpA and rmpA2 genes in the absence of c-rmpA could be a reason for the negative hypermucoviscosity phenotype and low virulence in rmpA-positive K. pneumoniae.
No preview · Article · Apr 2015 · Journal of Global Antimicrobial Resistance
[Show abstract][Hide abstract] ABSTRACT: Invasive syndrome caused by Klebsiella pneumoniae (KP), including liver abscess, is mainly caused by community-acquired strains with characteristics of positive hypermucoviscosity (HV) phenotype and regulator of mucoid phenotype A (rmpA) and transcriptional activator (rmpA2) genes. Extended- spectrum β-lactamase-producing KP (ESBL-KP) is commonly nosocomial and rarely HV-positive. We aimed to explore the reasons of the rarer prevalence of HV phenotype, rmpA and rmpA2 as well as the virulence phenotype among the ESBL-KP isolates from clinical specimens than those non-ESBL isolates. The β-lactamase genes, rmpA, rmpA2 and genes for K capsule serotype of 440 KP isolates were analyzed. The virulence of the isolates was characterized by the mouse lethality experiments. The prevalence rates of HV phenotype (˜50% vs. < 10%) as well as rmpA and rmpA2 genes (˜ 50-60% vs. < 20-30%) were significantly higher in non-ESBL group than in the ESBL group (p < 0.0001). Expression of HV phenotype in the rmpA-positive KP isolates was significantly rarer in the ESBL group than in non-ESBL group (33.3% vs. 91.9%, p < 0.0001). The frameshift mutations of rmpA and/or rmpA2 corresponded to negative HV phenotype of KP isolates that harbored the rmpA and/or rmpA2, resulting in variable mouse lethality (LD50, ˜10(3) - >5x10(7) CFU). The mutation rates might significantly differ among KP isolates from various sources. Virulence was dependent on rmpA-related HV phenotype. In conclusion, ESBL-KP isolates were less hypermucoviscous and less virulent than non-ESBL KP isolates, mostly due to concurrently lower carriage and higher mutation rates of the rmpA and rmpA2 genes.
[Show abstract][Hide abstract] ABSTRACT: BackgroundThis study was conducted to investigate an outbreak caused by imipenem-resistant Acinetobacter baumannii (IRAB) in a medical intensive care unit (ICU) in a regional hospital.MethodsIn response to an IRAB outbreak from October 2012 to February 2013, we developed several infection control measures, including an extensive review process of environmental cleaning and disinfection, and used molecular methods to identify each clinical and environmental IRAB isolate.ResultsDuring this five-month period, 22 patients were colonized with IRAB and 18 patients had IRAB infections. The in-hospital mortality rate was significantly higher among patients with infections rather than colonizations (44.4% vs 9.1%, p = 0.028). Additionally, nine environmental specimens, including five specimens collected after terminal disinfection, were positive for IRAB. 12 environmental isolates and 28 of 36 available clinical isolates belonged to one unique pulsotype A, which was confirmed by molecular methods. We found the concentration of disinfectant, 0.08% sodium hypochlorite, was inadequate. After correcting the environmental cleansing methods, the surveillance study showed no further IRAB isolates on the control panel surfaces of the medical equipment or in patients in the ICU. Additionally, an in
vitro study of IRAB immersed in different concentrations of sodium hypochlorite showed that 0.5% sodium hypochlorite eradicates IRAB after 30 seconds of inoculation, but 0.08% sodium hypochlorite only reduces the bacterial load.ConclusionsThis study highlights the importance of the preparation of disinfectants to adequately achieve environmental disinfection in the control of IRAB outbreaks in the ICU.
[Show abstract][Hide abstract] ABSTRACT: In this study, we designed a novel colorimetric method to detect multidrug resistance in Mycobacterium tuberculosis isolates. The assay of loop-mediated isothermal amplification (LAMP) is used to amplify target DNA from multidrug-resistant M. tuberculosis isolates, and enzyme-linked immunosorbent assay (ELISA) is used for the colorimetric determination. This method is designed based on point mutation at the hot spot region in target drug-resistant gene using LAMP-polymerase chain reaction (PCR), hybridization, and thermal melting for differentiating homoduplex DNA (drug-susceptible stain) and heteroduplex DNA (resistance mutant). From ELISA colorimetric detection, color change developed in drug-susceptible strains, and colorless result appeared in resistance mutants. A comparison of this LAMP-PCR-hybridization–thermal melt–ELISA (LAMP–TM–ELISA) method with the automated BACTEC MGIT 960 system showed that the sensitivity of this molecular analysis of resistance to isoniazid, rifampin, amikacin, and ciprofloxacin in M. tuberculosis was 92.3%, 95.3%, 93.1%, and 91.4%, respectively. This method for detection of resistance to isoniazid, rifampin, amikacin, and ciprofloxacin in M. tuberculosis showed a specificity of 95.5–98.2% and a test efficiency of 93.2–96.8%. This LAMP–TM–ELISA method will be a useful tool for rapid diagnosis (within 1 working day) and cost-effectiveness (US$15/reaction) to detect resistance to isoniazid, rifampin, amikacin, and ciprofloxacin via katG, inhA and mabA-inhA promoter, rpoB, rrs, gyrA, and gyrB genes in M. tuberculosis isolates.
No preview · Article · Sep 2014 · Biomarkers and Genomic Medicine
[Show abstract][Hide abstract] ABSTRACT: In this study, detection and characterization of class 1 integron-associated gene cassettes from Pseudomonas aeruginosa isolates in southern Taiwan were investigated. The study focused on the association between integron-associated resistance gene cassettes and multidrug resistance in P. aeruginosa isolates. Using polymerase chain reaction amplification, DNA sequencing, and basic local alignment search tool analysis, a total of 22 different types of gene cassette arrays were detected in 162 class 1 integron-positive P. aeruginosa isolates. We first identified 11 different types of new gene cassette arrays within class 1 integron in P. aeruginosa isolates, including aac(6′)-II-catB2-aadA2, aac(6′)-II-aadA2, aac(6′)-II-catB2, aacA4-aadA15, aacC1-orfA-orfB-aadA1, cm1A-aadA1, catB3-blaOxA-10-aadA15, aacA4-catB8-aadA1, aadB-orfF1-aadA11, dfrB1, and dfrB4a-aacA4-aacA4-aadA1. Of these, aac(6′)-II-catB2-aadA2 was the most frequently found gene cassette. Twenty-one (21/162, 12.9%) strains carrying two different types of gene cassette arrays of catB3-blaOxA-10-aadA15 and aac(6′)-II-catB2-aadA2 were also simultaneously present in the P. aeruginosa isolates. A novel dfrB4a gene, different from the dfrB4 gene detected in the gene cassette array of dfrB4a-aacA4-aacA4-aadA, was characterized. A metallo-β-lactamaseo gene was also found to be carried on the gene cassette of blaVIM-3-orf2a-aacA4-aadB-aacA4 inserted in a class 1 integron obtained from meropenem-resistant P. aeruginosa isolates.
No preview · Article · Jun 2014 · Biomarkers and Genomic Medicine
[Show abstract][Hide abstract] ABSTRACT: Mutations in the quinolone resistance-determining regions (QRDRs) of gyrA, gyrB, parC, and parE have been characterized among the 232 isolates of ciprofloxacin (CIP)-resistant Pseudomonas aeruginosa. As expected, no mutations in the QRDRs of four target genes were detected in the CIP-susceptible isolates of P. aeruginosa. It was noted that P. aeruginosa showing no mutation in the QRDRs of target genes were frequently found in isolates with a CIP in minimal inhibitory concentration (MIC) = 2 μg/mL than those of isolates with a CIP in MIC ≥4 μg/mL. The prevalence of P. aeruginosa with no mutations in the QRDRs of target genes is higher in isolates only resistant to CIP than in isolates resistant to CIP and other drugs. Double mutations occurring in gyrA and parC genes associated with a high-level resistance to CIP in MICs ≥4 μg/mL were found in 101 out of 176 isolates. Furthermore, mutations in parC and parE joined with mutation in gyrA were commonly found in P. aeruginosa highly resistant to CIP.
No preview · Article · Jun 2014 · Biomarkers and Genomic Medicine
[Show abstract][Hide abstract] ABSTRACT: The widespread multidrug-resistant Enterobacteriaceae pose a serious therapeutic challenge. Colistin and tigecycline are potential antimicrobial agents for treating infections caused by extended-spectrum β-lactamase (ESBL)-producing Enterobacteriaceae. We evaluated the in-vitro activity of colistin sulfate against 253 ESBL producers isolated from patients admitted to a medical center in southern Taiwan (Escherichia coli, n = 82; Klebsiella pneumoniae, n = 102; Enterobacter cloacae, n = 34; and Serratia marcescens, n = 35). Colistin showed promising in-vitro activity against E. coli, K. pneumoniae, and E. cloacae, but not S. marcescens. One ESBL-producing K. pneumoniae strain with resistance to carbapenems (ertapenem, imipenem, and meropenem) was selected for time-killing studies. A combination of colistin and tigecycline showed synergism, but there was an inoculum effect. In conclusion, colistin was active against most ESBL-producing Enterobacteriaceae, and a combination of colistin with tigecycline was synergistic against some highly resistant strains, even those with carbapenem resistance.
Full-text · Article · Dec 2013 · Journal of microbiology, immunology, and infection = Wei mian yu gan ran za zhi
[Show abstract][Hide abstract] ABSTRACT: Infections due to Prototheca spp. are ubiquitous in nature, occurring in both immunocompetent and immunocompromised patients. The study cohort consisted of 14 cases of Prototheca algaemia reported over the past 5 decades and 2 recent cases from study hospitals. Prototheca wickerhamii was the most common species. The overall mortality rate was 62.5%. Prototheca algaemia, a healthcare-associated infection, was observed in immunocompromised patients and was associated with a poor prognosis.
[Show abstract][Hide abstract] ABSTRACT: Vibrio vulnificus typically causes septicemia and necrotic wound infection. Among V vulnificus–related complications, acute nonthromboti myocardial damage has not been reported. The most effective antibiotic treatment of V vulnificus infection includes combination of a third-generation cephalosporin and a tetracycline or its analogue.
However, recommendations of a fourth-generation cephalosporinbased regimen for treating the disease are not established. A 67-yearold diabetic man acquired V vulnificus infection via a fish-stunning wound on the right foot. The patients developed septicemia and
hemorrhagic bullous necrotic wounds and followed by acute nonthrombotic cardiac injury with low cardiac output. After initial resuscitation, we applied dobutamine inotropic therapy with combination of cefpirome and ciprofloxacin or minocycline, which achieved
a good clinical outcome.
No preview · Article · Oct 2013 · The American journal of emergency medicine