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Diagnostic microbiology and infectious disease 03/2013; · 2.45 Impact Factor
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ABSTRACT: A total of 123 Shigella isolates were collected from SiXian area in Anhui, China. Screening was carried out by polymerase chain reaction (PCR) amplification of plasmid-mediated quinolone resistance (PMQR) determinants. Different β-blactamases genes, plasmid-borne bla(AmpC), 16S rRNA methylase genes, integrons, and mutations in quinolone resistance-determining regions were analysed by PCR for the PMQR-positive isolates.
Diagnostic microbiology and infectious disease 03/2013; 75(3):327-9. · 2.45 Impact Factor
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ABSTRACT: Serratia marcescens, a Gram-negative bacillus that belongs to the family Enterobacteriaceae, is an opportunistic pathogen that can cause many types of nosocomial infections (1).…
Antimicrobial Agents and Chemotherapy 08/2012; 56(10):5426-7. · 4.84 Impact Factor
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The Journal of Antibiotics 08/2012; · 1.65 Impact Factor
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ABSTRACT: To test the mutant selection window (MSW) hypothesis with Staphylococcus aureus exposed to vancomycin in an animal model and to compare in vivo and in vitro exposures that restrict the enrichment of resistant mutants.
Local infection with S. aureus was established in rabbits, and the infected animals were treated with various doses of twice-daily vancomycin (half-life 6 h) for 3consecutive days to provide antibiotic concentrations below the MIC, between the MIC and the mutant prevention concentration (MPC), and above the MPC. Changes in susceptibility and the numbers of surviving organisms were monitored daily on agar plates containing 2× and 4× MIC of vancomycin.
S. aureus lost vancomycin susceptibility when drug concentrations at the site of infection fluctuated between the lower and upper boundaries of the MSW, defined in vitro as the MIC(99) and the MPC, respectively. Both boundaries were determined in vitro, before starting animal studies. The value at which resistant mutants are not enriched in vivo was estimated as an AUC(24)/MPC value of ∼15 h, where AUC(24) is the area under the drug concentration time curve in a 24 h interval. The estimated anti-mutant AUC/MIC ratio in vivo was ≥200 h.
These findings support the MSW hypothesis and the anti-mutant AUC/MIC ratio estimated in vivo is consistent with that reported in in vitro studies. Keeping vancomycin concentrations above the MPC or AUC(24)/MPC >15 h is a straightforward way to restrict the acquisition of resistance.
Journal of Antimicrobial Chemotherapy 07/2012; 67(11):2700-6. · 5.07 Impact Factor
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ABSTRACT: We investigated the prevalence of plasmid-mediated quinolone resistance (PMQR) determinants and examined the association of these determinants with extended-spectrum β-lactamases (ESBLs) and/or plasmid-mediated AmpC β-lactamases (pAmpCs) in Serratia marcescens isolates in China. In this study, the presence of PMQR determinants was significantly related to the coproduction of ESBLs and/or pAmpCs (CTX-M-14, SHV-5, DHA-1, and ACT-1), among which CTX-M-14 was the most common gene type.
Antimicrobial Agents and Chemotherapy 06/2012; 56(8):4529-31. · 4.84 Impact Factor
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ABSTRACT: Clinical failures with vancomycin against meticillin-resistant Staphylococcus aureus (MRSA) infections have challenged vancomycin's standing as a first-line antimicrobial for these infections. Conventional MIC tests were not predictive of the in vivo therapeutic effect of vancomycin. Thus, we tested the susceptibility for the resistant mutants in the mutant selection window of S. aureus ATCC43300 (a MRSA strain) by three different MIC-testing methods in this paper. The MIC of vancomycin was estimated at 2 μg ml⁻¹ on the Mueller-Hinton agar (MHA) plate only for the resistant mutant that was selected from the plate of vancomycin concentration 12 μg ml⁻¹. The obvious changes of susceptibility testing were found between the resistant mutants and S. aureus ATCC43300 on the Brain-Heart Infusion Agar (BHIA) plates. There were subtle changes in the MIC trend within the susceptible range with the result of Etest for the resistant mutants. The susceptibility for the subcultures of resistant mutants would fall back when the external drug environment disappeared. In comparison with the S. aureus ATCC43300, sequence analysis revealed that there were no mutations in the staphylococcal protein A (spa) sequencing of the resistant mutants. The spa tape is t421 for all isolates.
The Journal of Antibiotics 04/2012; 65(6):307-10. · 1.65 Impact Factor
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Jing Sun,
Li-Fen Hu,
Min Wang,
Wei Shi,
Xi-Hai Xu, Jun Cheng,
Tai Ma,
Xiao-Ming Luo,
Zhong-Xin Wang,
Ying Ye,
Jia-Bin Li
The Brazilian journal of infectious diseases: an official publication of the Brazilian Society of Infectious Diseases 02/2012; 16(1):109-10. · 0.55 Impact Factor
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ABSTRACT: The purpose of this study was to investigate the phenotypic and molecular characterization of a novel plasmid-mediated AmpC-type β-lactamase in Klebsiella pneumoniae E701 isolated from Anhui province in China. In comparison with the ACT-1, sequence analysis revealed that there were 43 point mutations in the coding gene, and 10 of which led to amino-acid substitution. Resistance could be transferred by conjugation or transformation with plasmid DNA into E. coli JM109, which was due to the production of a β-lactamase with an isoelectric point of 8.4 named ACT-6. Cloning, expression, purification and kinetics were carried out to study the characterization of the novel AmpC-type β-lactamase. The results of MIC determinations and substrate profiles showed there was no significant difference in the activities of the novel enzyme and ACT-1. Moreover, the class 1 integron and the whole open reading frame of the novel AmpC-type β-lactamase from K.pneumoniae E701 were detectable in the same size plasmid. This is the first report on the emergence of the novel ACT-6 type β-lactamases in K. pneumoniae.
The Journal of Antibiotics 02/2011; 64(4):317-20. · 1.65 Impact Factor
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ABSTRACT: To retrospectively investigate the risk factors, distribution, antibiotic resistance of infection with Gram-positive (G+) bacteria in an intensive care unit (ICU), so as to provide the reference for clinical prevention and treatment.
A retrospective analysis of clinical data of 83 patients with G+ bacteria infection in ICU from January 2003 to December 2008 was done.
Of the 125 strains of G+ bacteria from 83 patients, Staphylococcus was the main organism (63.2%, 79/125). The prognosis of the patient was related with surgical operation (chi2=9.107, P=0.003), gastric intubation (chi2=4.053, P=0.044), complication (chi2 5.908, P=0.015) and the use of immunosuppressant (chi2=5.761, P=0.016). Multi-bacterial infection was related with surgery (chi2=8.847, P=0.003) and tracheostomy (chi2=10.445, P=0.001). The antibiotic susceptibility test in vitro showed that G+ bacteria displayed multi-resistance to antibiotics, but all of G+ bacteria were sensitive to vancomycin (resistance rate was 0).
Staphylococcus was the most common pathogen of G+ bacterial infection in ICU. Further surveillance of bacterial resistance is warranted in ICU, and antimicrobial drugs should be used according to the result of susceptibility test. Taking account of the antibiotic resistance and risk factors of G+ bacteria infection in ICU, the infection could be controlled and the death rate could be cut down when appropriate measures are taken.
Zhongguo wei zhong bing ji jiu yi xue = Chinese critical care medicine = Zhongguo weizhongbing jijiuyixue 08/2010; 22(8):451-4.
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ABSTRACT: To study the risk factors of infection of extended-spectrum beta-lactamases (ESBL)-producing strains and drug resistance of Enterobacteriaceae that infected burn patients.
A retrospective study was performed on clinical information of 92 patients with Enterobacteriaceae infection in our burn unit from January 2001 to December 2008. The distribution and drug resistance of Enterobacteriaceae, and the detection rate, drug resistance of ESBL-producing strains, and its risk factors of nosocomial infection were analyzed. Data were processed with Chi-square test.
One hundred and nine strains of Enterobacteriaceae were isolated, with 38 (34.9%) strains of Enterobacter cloacae, 25 (22.9%) strains of Escherichia coli, 22 (20.2%) strains of Klebsiella pneumoniae, 13 (11.9%) strains of Proteus mirabilis, and 11 (10.1%) other strains of Enterobacteriaceae. Enterobacteriaceae were moderately or highly resistant to antibiotics except imipenem, resistance rate of which was less than 8.0%. ESBL-producing strains accounted for 44.0% in Escherichia coli, and 77.3% in Klebsiella pneumoniae. Drug-resistance rate of ESBL-producing strains to antibiotics was obviously higher than that of non ESBL-producing strains. Length of hospital stay longer than 20 days, and use of the third-generation cephalosporin longer than 5 days, quinolone antibiotics longer than 7 days, and topical antibiotics longer than 5 days were the risk factors of nosocomial infection caused by ESBL-producing strains, comparing with non ESBL-producing strains, the difference was statistically significant (with chi2 value respectively 5.491, 4.441, 15.186, 4.938, P values all below 0.05).
Enterobacteriaceae strains in burn unit of our hospital are highly drug resistant, with high lactamase-producing rates, calling for intense monitor to control the risk factors that predispose the infection of ESBL-producing strains in order to lower the infection rate.
Zhonghua shao shang za zhi = Zhonghua shaoshang zazhi = Chinese journal of burns 06/2010; 26(3):199-201.
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ABSTRACT: To explore the status of methicillin-resistant Staphylococcus aureus (MRSA) infection in an intensive care unit (ICU), and investigate the active efflux mechanism of MRSA.
Eighty isolates were identified as MRSA among 102 strains of Staphylococcus aureus collected, and then the minimal inhibitory concentration (MIC) were determined. The 4 primers of active efflux gene were designed to amplify the 80 clinical isolates respectively by polymerase chain reaction (PCR). The PCR products were analyzed by electrophoresis in order to grasp the situation of the existence of the four genes (norA, qacA, qacB and qacJ). Omeprazole inhibition test was used to observe the changes in the susceptibility of MRSA to antibiotics.
The detection rate of MRSA was 78.4%. The sensitivity rate of MRSA to both vancomycin and teicoplanin was 100.0%, while to other antibiotics (oxacillin, benzylpenicillin, cefuroxime, cefotaxime, ceftazidime, ceftiaxone, cefepime, cefoxitin, imipenem, piperacillin and tazobactam, azithromycin, erythromycin, chloramphenicol, clindamycin, amikacin, gentamicin, levofloxacin, gatifloxacin, ciprofloxacin) MRSA was multi-drug resistant. The detection rates of norA, qacA, qacB and qacJ were 67.5% (54/80), 15.0% (12/80), 21.2% (17/80) and 11.2% (9/80), respectively. Combined use of omeprazole and levofloxacin could lower MIC value.
The infection of MRSA in ICU is serious. MRSA is multi-drug resistant and possesses active efflux genes norA, qacA, qacB and qacJ. Omeprazole can inhibit the activity of the active efflux genes.
Zhongguo wei zhong bing ji jiu yi xue = Chinese critical care medicine = Zhongguo weizhongbing jijiuyixue 12/2009; 21(12):722-5.
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ABSTRACT: Three clinical strains of Escherichia coli (p168, p517 and p667) were collected in 2006 from three hospitals in Anhui Province (China). PCR and DNA sequencing revealed that E. coli p168 carried a novel extended-spectrum beta-lactamase (ESBL), which was designated CTX-M-87. The extended-spectrum beta-lactamase which was carried by E. coli p517 and E. coli p667 was previously named CTX-M-65. The deduced amino acid sequence of CTX-M-87, with pI 9.1, differed from that of CTX-M-14 by the substitutions Ala77-->Val and Pro167-->Leu. Like CTX-M-14, CTX-M-87 had a more potent hydrolytic activity against cefotaxime than against ceftazidime and had high affinity for cefuroxime and cefotaxime. These data show that mutations at position 167 in CTX-M do not always affect catalytic activity and substrate preference.
Journal of Medical Microbiology 07/2009; 58(Pt 6):811-5. · 2.50 Impact Factor
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ABSTRACT: This study reports phenotypic and molecular characterization of a novel CTX-M beta-lactamase carried by two Klebsiella pneumoniae isolates collected from two hospitals in China. Conjugation experiment, Southern hybridization, susceptibility testing, isoelectric focusing, PCR, and sequencing techniques as well as clone, expression, purification and kinetics were carried out to describe the characterization of the novel CTX-M-type enzyme. The analyses of plasmid profiling and pulsed-field gel electrophoresis of the novel enzyme were performed to investigate epidemiology. The PCR products had 967 nucleotides and a novel CTX-M enzyme with a pI of 8.5 was implicated in this resistance: CTX-M-72. Two strains exhibited a clavulanic acid-inhibited substrate profile that included extended-spectrum cephalosporins. The amino acid sequence of the CTX-M-72 beta-lactamase differed from that of the CTX-M-3 beta-lactamase by the Arg-->Gly change at position 164. The novel enzyme was susceptible to ceftazidime, the same response being observed for other CTX-M enzymes. The substrates of the beta-lactamase were also characterized. Furthermore, two resistant genes of clinical strains were closely related. The emergence of a novel CTX-M-type extended-spectrum beta-lactamase was rarely described in other areas. This study illustrated the importance of molecular surveillance in tracking CTX-M-producing strains in large teaching hospitals, suggested the horizontal transfer of plasmid-borne bla(CTX-M) genes contributed to the dissemination of CTX-M enzymes in hospital environments, and emphasized the need for epidemiological monitoring.
The Journal of General and Applied Microbiology 06/2009; 55(3):207-16. · 0.98 Impact Factor
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ABSTRACT: Two clinical strains (Klebsiella pneumoniae 516 and K. pneumoniae 1335) collected in September 2006 from different hospitals in Anhui Province (China) harboured two novel plasmid-mediated bla(CTX-M) genes, designated bla(CTX-M-80) and bla(CTX-M-81), respectively. Both CTX-M-80 with pI of 9.0 and CTX-M-81 with pI of 8.4 were extended-spectrum beta-lactamases (ESBLs). The results of susceptibility testing demonstrated two enzymes were highly activity against broad spectrum beta-lactams, but the level of resistance was reduced with the addition of beta-lactamase inhibitors. The bla(CTX-M-80) gene was detected on a 110-kb plasmid and the bla(CTX-M-81) gene existed on a 120-kb plasmid. The deduced amino acid sequence of CTX-M-80 differed from that of CTX-M-3 by the substitution Ala-27-->Val, and CTX-M-81 possessed the Lys-->Glu, Lys-->Gln, and Asn-->His changes at respective position 82, 98, and 132 in compassion with CTX-M-14. The enzymatic properties showed CTX-M-80 and CTX-M-81 had higher affinities for penicillin G (lower Km values) than for cephalosporins. The activities of novel enzymes against ceftazidime were undetectable or limited, as indicated by MICs data, the same response being observed for many other CTX-M enzymes. This report was evidence of the diversity of CTX-M-type ESBLs in China.
Molecular Biology Reports 03/2009; 37(3):1261-7. · 2.93 Impact Factor
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International Journal of Antimicrobial Agents 10/2008; 33(1):95-6. · 4.13 Impact Factor
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ABSTRACT: The aim of this work was to study the phenotypic and molecular characterization of a novel plasmid-mediated AmpC beta-lactamase from Escherichia coli E384. Conjugation experiments, isoelectric focusing, pulsed-field gel electrophoresis, plasmid profiling, and Southern blot as well as PCR, sequencing techniques, and susceptibility testing were carried out to investigate the underlying mechanism of resistance. The kinetic parameters were determined to characterize the novel enzyme. MIR-4 beta-lactamase, pI 8.2, is a novel variant with four substitutions of amino acids compared with the sequence of MIR-1. E. coli E384 displays resistance to eight beta-lactam antimicrobial agents and three fluoroquinolones. The minimal inhibitory concentrations of beta-lactam in combination with beta-lactamase inhibitors show no significant synergy. Kinetic parameters suggest that the novel enzyme effectively hydrolyzes broad-spectrum beta-lactams. The same hybridization signal was detectable only in the 54-kb plasmid band that hybridized with the bla (CTX-M)- and bla(ampC)-specific probes. This is the first description of a plasmid-mediated MIR-4 enzyme in China. This study illustrates the importance of molecular surveillance in tracking AmpC-producing strains at general hospitals and emphasizes the need for epidemiological monitoring.
Current Microbiology 10/2008; 57(6):558-63. · 1.82 Impact Factor
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ABSTRACT: This study investigated the phenotypic and genetic properties of 28 clinical isolates of metallo-beta-lactamase (MBL)-producing Chryseobacterium indologenes recovered from a university hospital. Twenty isolates were confirmed to carry a bla(IND) gene. Among them, 9 isolates were confirmed to carry the IND-1 gene, 10 contained the IND-2 gene and 1 had bla(IND-3) alleles. One strain (No. 7) confirmed to be carrying the bla(IND-1) gene was susceptible to imipenem and was negative in phenotypic methods. The data revealed that the antimicrobial resistance patterns of C. indologenes harbouring MBL genes are remarkably distinct. Two specific types of MBL genes, bla(IND-1) and bla(IND-2), were identified to be the major genotype for C. indologenes isolated from Hefei, China.
International Journal of Antimicrobial Agents 09/2008; 32(5):398-400. · 4.13 Impact Factor
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ABSTRACT: Two clinical strains of Klebsiella pneumoniae (K. pneumoniae) and one isolate of Escherichia coli (E. coli) were collected from two large general hospitals in China. Conjugation experiment, susceptibility testing, isoelectric focusing, PCR, and sequencing techniques as well as clone, expression, purification and kinetics were carried out to describe the characterization of the novel SHV-tpye enzyme. The analysis of plasmid profiling and pulsed-field gel electrophoresis of the novel enzyme were performed to investigate epidemiology. These isolates had CTX-M-14 and SHV-89 beta-lactamases. SHV-89 beta-lactamase of pI 7.6 is a novel variant with two substitutions compared with the sequence of SHV-1: Leu35Gln and Met129Val. Its gene also had two silent mutations at positions 369 and 774, respectively. The results of substrate profiles and MIC determinations showed the activity of the novel enzyme was insufficient for the enzyme to count as an extended-spectrum beta-lactamase (ESBL). The substrates of the enzyme were also characterized. Furthermore, the three novel SHV enzyme-producing strains were epidemiologically unrelated. The emergence of a novel SHV-type beta-lactamase is rarely described in other areas. This study illustrates the importance of molecular survelliance in tracking SHV-producing strains in large teaching hospitals and emphasizes the need for epidemiological monitoring.
Molecular Biology Reports 07/2008; 36(5):1141-8. · 2.93 Impact Factor
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ABSTRACT: The aim of the present study was to study the phenotypic and molecular characterization of 5 novel CTX-M-beta-1actamases carried by 5 Klebsiella pneumoniae isolates and 3 Escherichia coli isolates collected from 4 hospitals in Hefei, China.
The purified PCR products were ligated with pGEM-Teasy vectors, expressed, and sequenced. The complete genes of the CTX-M-beta-lactamases were ligated with the pHSG398 vector to express prokaryotic recombinant proteins. Plasmids were extracted by rapid alkaline lysis protocol, and the PCR method was performed to determine whether the prokaryotic expression was successful or not. Antimicrobial susceptibility was tested and the phenotypes of transformants were determined according to criteria recommended by the Clinical and Laboratory Standards Institute. The kinetic parameters of enzymes were confirmed. The isoelectric points (pI) were determined by isoelectric focusing assay. Pulsed-field gel electrophoresis and plasmid profiling were performed.
The PCR products had 1101 nucleotides and were determined as CTX-M-46, CTX-M-47, CTX-M-48, CTX-M-49, and CTX-M-50. All strains were resistant to cefotaxime, but most of them were susceptible or intermediate to ceftazidime. The phenotypes of novel enzymes were determined as extended-spectrum-beta-lactamases (ESBL). Penicillin G, cephalothin, cefuroxime, and cefotaxime were determined to good substrates, whereas ceftazidime hydrolysis was not detected. The pI of the 5 novel CTX-M-beta-lactamases were 8.0. CTX-M-derivatives could be the multiplex genesis in our area.
This is the first report of these 5 novel plasmid-mediated CTX-M ESBL produced from China in the world. Molecular typing reveals notably different origin in genes encoding different CTX-M variants of 8 strains.
Acta Pharmacologica Sinica 03/2008; 29(2):217-25. · 1.95 Impact Factor
