Study on the genotypes of TEM-like and SHV-like extended-spectrum beta-lactamases in clinical isolates of Gram-negative bacilli in Guangzhou / 中华检验医学杂志

ABSTRACT

Objective To investigate the main genotypes and the epidemic characteristics of TEM-type and SHV-type extended-spectrum beta-lactamases (ESBLs) of the gram-negative bacilli in Guangzhou.Methods The phenotype of ESBLs from 3 500 clinical isolates were primary screened and confirmed by the NCCLS confirmatory test according to guidelines of NCCLS(2001). PCR were performed on 3 500 clinical isolates using primers specific for blaTEM and blaSHV, respectively, the PCR product were purified and sequenced by ABI prism 377 DNA sequencer.Results Total of 3 500 un-replicated and consecutive Gram-negative bacilli were isolated from 13 hospitals in Guangzhou in the past two years, and the prevalence of ESBLs-producing clinical Gram-negative isolates was 31.0%(1 084/3 500). The positive rates of PCR results for blaTEM, blaSHV, and both of them in all the clinical Gram-negative isolates were 24.0%(840/3 500),10.8%(378/3 500),and 3.7%(128/3 500), respectively. All PCR products for blaTEM were further identified as TEM-1-type non-ESBLs gene, including TEM-1,TEM-1B,TEM-1D,and TEM-1F,by DNA sequencing analyses. However, almost all of the blaSHV gene were further identified as SHV-type ESBLs gene(the prevalence of SHV-1 is 7.2% only).The prevalence of SHV-12/5a accounted for highest(50.0%,152/304) in Guangzhou. Our test also showed that 53%(340/641) of blaTEM-producers [JP2] were Escherichia coli, and 57.9%(176/304) of blaSHV-producers were Klebsiella pneumoniae.Conclusions [JP]We could conclude from above results that SHV-type ESBLs, especial SHV-12/5a, was the prevalent genotype of ESBLs of clinical gram-negative bacilli in Guangzhou. TEM-type ESBLs did not exist in our city. In addition, SHV-12/5a-producing strains probably were main epidemic strains in Guangzhou. As for detection of ESBLs with regular phenotype methods, there was possibility of false negative and false positive.