ABSTRACT
OBJECTIVE To detect AmpC ?-lactamases from isolates of extended spectrum ?-lactamases(ESBLs) positive Escherichia coli and Klebsiella pneumoniae,which were isolated from four hospitals in Hangzhou from 2005 to 2006,and to analyze the antimicrobial activity of clinically commonly used antibiotics in vitro.METHODS Amount of 324 ESBLs positive isolates including E.coli and K.pneumoniae were collected from Zhejiang Provincial People′s Hospital;1st Affiliated Hospital of Zhejiang University;2nd Affiliated Hospital of Zhejiang University and Hangzhou Traditional Chinese Medicine Hospital perspectivly.AmpC ?-lactamase was identified by disc screening testing and three dimensional test,and the genotypes of AmpC ?-lactamase were also determined by multiplex polymerase chain reaction(Multi-PCR).Minimal inhibitory concentrations(MICs) of ten clinically commonly used antibiotics were determined by agar dilution for AmpC ?-lactamases positive isolates,and the data were analyzed by WHONET 5.3.RESULTS AmpC ?-lactamase phenotype test revealed that 76 AmpC ?-lactamase positive isolates(23.5%) were identified among 324 ESBLs positive isolates of E.coli and K.pneumoniae from four hospitals in Huzhou.69.7% Of the AmpC ?-lactamase phenotype positive isolates were positively amplified by Multi-PCR.The value of MIC50 for carbapenem was lower 0.25 ?g/ml.We also found four carbapenem-resistant strains in this study.CONCLUSIONS We found that the incidence rate of AmpC ?-lactamase is high among the ESBLs producing E.coli and K.pneumoniae strains in Hangzhou.Carbapenem antibiotics have higher antimicrobial activity than other tested antibiotics.
ABSTRACT
Objective To compare the application of three automated microbiology identification and rapid susceptibility assessment systems,Vitek1,Viket2 and BD Phoenix,in detection of extended-spectrum beta-lactamases(ESBLs).Methods The genotypes of 67 clinical isolates of ESBLs-producing E.coli and K.phneumoniae,which were collected from the 1st and 2nd Affiliated Hospital of Zhejiang University,were determined by PCR amplification and sequencing.Meanwhile,these isolates were analyzed by the three automatic microbiology identification system,and the minimum inhibitory concentration(MIC)s for antibiotics were determined.Results Majority of the 67 isolates produced CTXM type of ESBL.Among them,CTX-M-14,CTX-M-22,CTX-M24 and CTX-M-3 were the most frequently detectable types.By using Vitek-AMS,60 isolates(89.6%)were detected to be ESBLs-producing.By using Vitek2,62 isolates(92.5%) were ESBLsproducing.No SHV-12,CTX-M-14 and SHV-28 were detected by the 3 automatic systems.The results of MICs analysis indicated these isolates showed either high resistance for multiple antibiotics or around the boundary areas of MICs test.Conclusions The three automatic analysis systems are able to provide a detectable rate of more than 98% for ESBLs.However,it is needed to further improve the detection for high resistant strain or the strains carrying multiple resistant genes.