Resistance and genotyping of extended-spectrum β-lactamase-producing Escherichia coli isolates

Objective To detetct the production of extended spectrum β-lactamases(ESBLs) and the prevalence of CTX-M type,TEM-,SHV gene in E.coli.Methods Double-disk test and phenotypic confirmatory test were used to detect ESBLs in the E.coli strains isolated from clinical specimens.Polymerase chain reaction(PCR) was applied to identify CTX-M,TEM and SHV genotype.DNA sequence analysis was utilized to confirm the TEM and SHV gene subtypes.Results The overall prevalence of ESBLs-producing strains in E.coli isolates was 54.2%(45/83).CTX-M-type ESBLs was produced in 44 of 83 isolates(53.0%),TEM type ESBLs in 32 of 83 isolates(38.6%).and SHV type ESBLs in only 1 isolates(1.2%).No imipenem - or meropenem-resistant strain was found.The ESBLs-producing strains showed lower resistance to amikacin,piperacillin -tazobactam.cefepime.About 13.3%,17.8%,31.1%of the strains were resistant to these antibiotics,respective.y.More than 60%of the ESBLs-producing strains were resistant to trimethoprim-sulfamethoxazole,ievofloxacin,ciprofloxacin or gentamicin. Conclusions CTX-M group was the main ESBLs genotype.ESBLs-producing E.coli are usually multiple drug resistant.