CTX-M-14 and CTX-M-15 enzymes are the dominant type of extended-spectrum {beta}-lactamase in clinical isolates of Escherichia coli from Korea

1 Department of Laboratory Medicine, Hallym University College of Medicine, 150-950, 948-1 Daerim 1-Dong, Youngdeungpo-Gu, Seoul, Republic of Korea 2 Department of Laboratory Medicine, Kwandong University College of Medicine, 697-24 Whajung-Dong, Dukyang-Gu, Goyang, Republic of Korea 3 Department of Laboratory Medicine and Research Institute of Bacterial Resistance, Yonsei University College of Medicine, 120-752, 134 Shinchon-Dong, Seodaemu-Gu, Seoul, Republic of Korea 4 Research Institute for Antimicrobial Resistance, Kosin University College of Medicine, 602-030, 34 Amnam-Dong, Suh-Gu, Busan, Republic of Korea 5 Department of Laboratory Medicine, Hallym University College of Medicine, 134-701, 150 Sungnae-Gil, Kangdong-Gu, Seoul, Republic of Korea 6 Center for Food Safety Evaluation, Korea Food and Drug Administration, 122-704, 231 Jinheung-Ro, Eunpyung-Gu, Seoul, Republic of Korea Correspondence Seok Hoon Jeong kscpjsh{at}yuhs.ac Received June 30, 2008 Accepted October 27, 2008 This study was performed to assess the prevalence and genotypes of plasmid-borne extended-spectrum β -lactamases (ESBLs) and AmpC β -lactamases in Escherichia coli in Korea. A total of 576 isolates of E. coli was collected from 12 Korean hospitals during May and July 2007. A phenotypic confirmatory test detected ESBLs in 82 (14.2 %) of the 576 E. coli isolates. The most common types of ESBLs identified were CTX-M-14 ( n =32) and CTX-M-15 ( n =27). The prevalence and diversity of the CTX-M mutants, including CTX-M-15, CTX-M-27 and CTX-M-57, with significant hydrolytic activity against ceftazidime were increased. PCR experiments detected genes encoding plasmid-borne AmpC β -lactamases in 15/56 cefoxitin-intermediate or cefoxitin-resistant isolates, and the most common type of AmpC β -lactamase identified was DHA-1 ( n =10). These data suggest that the incidence of ESBLs in E. coli has increased as a result of the dissemination of CTX-M enzymes in Korea. In addition, CTX-M-22, CTX-M-27 and CTX-M-57 have appeared in Korea. Abbreviations: BA, boronic acid; CA, clavulanic acid; CAZ, ceftazidime; CTX, cefotaxime; ESBL, extended-spectrum β -lactamase; FOX, cefoxitin.