3 세대 세파계 항생제에 내성인 임상균주의 분포와 PCR 법을 이용한 TEM type beta-lactamase 생산균주의 동정

Prevalence of Strains Resistant to the Third Generation Cephalosporins among Clinical Isolates and Identification of TEM Type beta-lactamase from Resistant Strains by PCR Method

Compared to the first-and second-generation cephalosporins, the third-generation cephalosporins are remarkably stable against hydrolysis by the beta-lactamases produced by aerobic gram-negative bacilli, such as Enterobacteriaceae. Among these bacteria, the most prevalent plasmid-encoded beta-lactamase is TEM-1 beta-lactamase belonging to class A or group 2b. This enzyme is produced constitutively and is principally active against penicillins and old cephalosporins rather than third-generation cephalosporins, carbapenems and monobactams. However, new TFM type beta-lactamases including TEM-9 and TEM-12 evolved through point mutations in a gene encoding beta-lactamase have been discovered from patients during chemotherapy. These beta-lactamases are known to be capable of hydrolyzing most of the third-generation cephalosporins. To study the prevalence of beta-lactamases from clinical isolates collected in Korea, the minimal inhibitory concentrations(MICs) of several third- generation cephalosporins against 628 clinical isolates were determined by agar dilution methods, and beta-lactamase-producing bacteria were isolated by use of cefinase disc. By polymerase chain reaction(PCR) method, clinical isolates harboring a gene for TEM type beta-lactamase were identified among the beta-lactamase producing strains. Twenty three percent of the clinical isolates was resistant to the third-generation cephalosporins, and more than 90% of resistant cells produced various beta-lactamases. TEM type beta-lactamases were dominant in gram-negative bacilli, such as Escherichia coli, Klebsiella pneumoniae, Enterobacter species. These results suggest the necessity of the development of new cephalosporins which are stable against beta-lactamases like TEM.