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Korean J Infect Dis. 1997 Mar;29(2):93-103. Korean. Original Article.
Pai H , Kim JM , Kwon YM , Lee K , Chong Y , Kim EC , Cho DT .
Department of Internal Medicine, Dankook University College of Medicine.
Department of Microbiology, Dankook University College of Medicine.
Department of Clinical Pathology, Yonsei University college of Medicine.
Department of Clinical Pathology, Seoul National University College of Medicine.
Department of Microbiology, Kyungpook National University School of Medicine.
Abstract

BACKGROUND: Extended-spectrum beta-lactamases (ESBLs) are plasmid-mediated enzymes that confer resistance to oxyimino-beta-lactams such as cefotaxime, ceftazidime, and aztreonam, antibiotics that were designed to be effective against strains producing known plasmid-determined beta-lactamases. METHODS: Fifty-seven isolates of ESBL producing K. pneumoniae which were collected from 3 hospitals in Korea were characterized. They either transferred ceftazidime resistance or showed clavulanic acid enhancement of oxyimino-beta-lactam susceptibility. Beta-lactamase production by clinical isolates and transconjugants were characterized by isoelectric focusing and MIC values of oxyimino-beta-lactam were determined by agar dilution method. We performed PCR and RFLP for further characterization of TEM-type ESBLs. RESULTS: The results showed that SHV-type ESBLs, especially SHV-5 and SHV-2 predominated, but TEM-4 and plasmid- mediated AmpC beta-lactamases (pI 8.0 and pI 8.4) were present as well: SHV-5, 26; SHV-2, 12; TEM-4, 9; plasmid-mediated AmpC type beta-lactamase (pI 8.0), 4; plasmid-mediated AmpC type beta-lactamase (pI 8.4), 1. Two isolates produced both TEM-4 and SHV-5, which showed higher MIC50 of cefotaxime, ceftazidime and aztreonam than those in the isolates producing TEM-4 or SHV-5. Three isolates produced both plasmid-mediated AmpC type beta-lactamases and other ESBLs, each one of TEM-4, SHV-2 and SHV-5. All of the isolates showed high resistance to cefoxitin, cefotaxime, ceftazidime and aztreonam. CONCLUSION: With these results we conclude that SHV-type ESBLs outnumber and plasmid-mediated AmpC type beta-lactamases are present in high frequency in Korea.

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