The characteristics of extended-spectrum beta-lactamases in Korean isolates of Enterobacteriaceae

Extended-spectrum beta-lactamases (ESBLs) in gram-negative organisms have been implicated as the enzymes responsible for resistance to oxyimino-cephalosporins. The incidence of ESBL- producers in Korean isolates of Escherichia coli and Klebsiella pneumoniae were in the range of 4.8 7.5% and 22.5 22.8%, respectively. The ESBL-producing isolates revealed variable levels of resistance to cefotaxime, ceftazidime and aztreonam. They also showed the elevated MIC values of non-beta-lactam antibiotics. SHV-12 and SHV-2a were the enzymes most frequently found in K. pneumoniae strains, but TEM-52 was the most prevalent in E. coli isolates. About 15% of ESBL-producing isolates of Enterobacteriaceae produced CMY-1 enzyme, which conferred resistance to cephamycins such as cefoxitin as well as oxyimino-cephalosporins. Thus, the most common types of ESBLs in Korea are TEM-52, SHV-12, SHV-2a, and CMY-1.

Analysis of extended-spectrum beta-lactamase TEM produced by Klebsiella Pneumoniae / 감염

BACKGROUND: The prevalence of extended-spectrum beta-lactamase(ESBL)-producing organisms has been increasing in Korea. We performed a study to characterize various TEM derivatives with clinical isolates of Klebsiella pneumoniae collected from 3 hospitals in Korea. METHODS: Fifty-seven isolates of ESBL-producing K. pneumoniae collected from 3 hospitals were screened by TEM-specific PCR for the carriage of TEM genes. Thirteen strains were found to have TEM-related genes. Eleven blaTEM genes were amplifed and sequenced. The transfer of resistance was tested by conjugation and isoelectric points of beta-lactamases were determined. MICs were measured to obtain a resistance pattern for each indivudual wild- type and transconjugant strain. The hydrolysis rate of TEM-52 was measured spectrophotometrically. RESULTS: Ten strains carried plasmid-mediated CTEM-52 gene, which sequence showed the substitution of 3 amino acids compared to that of TEM-1: 104 glutamic acid --> lysine (GAG --> AAG), 182 methionine --> threonine (ATG --> ACG), and 238 glycine --> serine (GGT --> AGT). MIC showed that TEM-52 mediated a resistance to ceftazidime and aztreonam at a lower level than to cefotaxime. TEM-52 enzyme hydrolyzed cefotaxime efficiently (Vmax, 340) and showed fairly weak activity for ceftazidime (Vmax, 15.1), but very weak activity for aztreonam. The gene of TEM-52 beta-lactamases was mediated by approximately 77-kb plasmids. CONCLUSION: From these results, we conclude that the TEM-52 beta-lactamase is a common TEM- type ESBL in K. pneumoniae in Korea.