Prevalence of extended-spectrum beta-lactamases among Escherichia coli and Klebsiella pneumoniae isolates in a tertiary care hospital.

Extended-spectrum beta-lactamases (ESBLs) continue to be a major problem in clinical setups the world over, conferring resistance to the expanded-spectrum cephalosporins. Knowledge about their prevalence is essential to guide towards appropriate antibiotic treatment. The aim of the present study is to determine the prevalence of ESBL producers among Escherichia coli and Klebsiella pneumoniae isolates at a tertiary care institution. A total of 357 clinical isolates comprising E. coli (n = 181) and K. pneumoniae (n = 176) were recovered from various clinical samples over a period of six months from April to September 2006. Antibiogram profile of these isolates was determined to commonly used antibiotics, along with screening for ESBL production by the screening test as recommended by the Clinical Laboratory Standards Institute (CLSI). Isolates which showed positive results with screening test were shortlisted for confirmatory tests of ESBL production. Two tests were performed: phenotypic confirmatory test with combination disk and the minimum inhibitory concentration (MIC) reduction test. Out of 357 isolates of E. coli and K. pneumoniae screened for ESBL production, 120 were found to be potential ESBL producers. Of these, 80 isolates were confirmed to be ESBL producers. Thus the prevalence of ESBL-producing isolates of E. coli and K. pneumoniae was found to be 22% (80 out of 357). This was significantly lower than the data available from other hospitals.