Characteristics of Extended-spectrum beta-lactamase of Escherichia coli Strains Isolated from Clinical Specimens / 대한임상병리학회지

ABSTRACT

BACKGROUND: Recently Escherichia coli isolates with extended-spectrum beta-lactamase(ESBL) have been increased in Korea. ESBLs confer variable levels of resistance to cefotaxime, ceftazidime and other broad-spectrum cephalosporins as well as to monobactams such as aztreonam, but they have no detectable activity against cephamycins and carbapenems. The aim of this study was to characterize the ESBL produced by E. coli strains isolated from clinical specimens. METHODS: From March to July, 1998, a total of 93 clinical isolates of E. coli, which was produced ESBL, were collected from patients of the Asan Medical Center. The isolates flagged as ESBL producers by microbroth dilution antibiotic susceptibility test were confirmed by the double disk synergy test. Minimal inhibitory concentration(MIC) of beta-lactams were determined by agar dilution method. The presence of TEM, SHV or CMY-1 gene was determined by polymerase chain reaction. The types of beta-lactamase gene were determined by isoelectric focusing and nucleotide sequence analysis. RESULTS: Sixty-two strains carried plasmid-mediated TEM-52 gene, which sequence showed the substitution of 3 amino acids compared to that of TEM-1. Seventeen strains produced SHV-12, six strains produced SHV-2a, three strains produced TEM-52 and SHV-12, three strains produced TEM-52 and SHV-2a, and one strain produced SHV-2a and SHV-12. One out of twenty-seven strains of cefoxitin-resistant E. coli was confirmed to have CMY-1 beta-lactamase by PCR and nucleotide sequence analysis. CONCLUSIONS: TEM-52 was the most prevalent in E. coli isolates. The most common SHV-types of ESBL in Korea are SHV-12 and SHV-2a in E. coli isolates. In Korea, widespread use of oxyimino-cephalosporins in the hospitals has dramatically increased the prevalence of ESBL-producers in E. coli. Therefore, more prudent use of antibiotics is necessary to reduce the spread of these resistant organisms.