Epidemiology of Plasmid-Mediated AmpC beta-Lactamase Produced by Clinical Isolates of Klebsiella pneumoniae from Four University Hospitals in Korea / 병원감염관리

ABSTRACT

BACKGROUND: Plasmid-mediated AmpC beta-lactamases (PABLs) are cephalosporinases that confer resistance to a wide variety of beta-lactam drugs and that may thereby create serious therapeutic problems. The PABL-producing organisms are a major concern in nosocomial infections and should therefore be monitored in surveillance studies. METHODS: During the period of May to July 2004, 27 cefoxitin non-susceptible isolates of Klebsiella pneumoniae from four university hospitals (Seoul 2, Daejeon 1, and Choongju 1) were tested for antimicrobial susceptibility by the broth microdilution method. The cefoxitin non-susceptible isolates were further investigated by the double disk synergy test for extended-spectrum beta-lactamases, multiplex AmpC PCR, DNA sequencing, and pulsed-field gel electrophoresis (PFGE). RESULTS: PABL-producing K. pneumoniae were found in all the four hospitals. Eight (32%) of 25 PABL producers were also tested positive by double disk synergy tests. Susceptibilities of the PABL producers were as follows ceftazidime, 4%; aztreonam, 36%; cefepime, 76%; and imipenem, 100%. Among the 25 K. pneumoniae isolates were 24 DHA-1 and 1 CMY-1 beta-lactamase producers. The PFGE patterns of the DHA-1-producing K. pneumoniae showed variable as well as identical patterns. CONCLUSION: PABL-producing K. pneumoniae is widespread among medical institutions in Korea. A DHA-1 type in K. pneumoniae was the predominant enzyme detected. Overall, despite many different PFGE patterns of the PABL producers, some outbreak and epidemic clones appear to be prevalent in some hospitals in Korea. For the prevention of the spread of PABL-producing K. pneumoniae, it should be identified accurately by the clinical laboratory.