Brief Communication DOI 10.3349/ymj.2011.52.2.351 pISSN: 0513-5796, eISSN: 1976-2437 Yonsei Med J 52(2):351-357, 2011 The Characteristics of Metallo-β-Lactamase-Producing Gram-Negative Bacilli Isolated from Sputum and Urine: A Single Center Experience in Korea Bum Sik Chin,1 Sang Hoon Han,1 Suk Hoon Choi,1 Han Sung Lee,1 Su Jin Jeong,1 Hee Kyung Choi,1 Jun Yong Choi,1 Young Goo Song,1 Chang Ki Kim,2 Dongeun Yong,2 Kyungwon Lee,² and June Myung Kim¹ ¹AIDS Research Institute and Department of Internal Medicine, Yonsei University College of Medicine, Seoul; ²Research Institute of Bacterial Resistance and Department of Laboratory Medicine, Yonsei University College of Medicine, Seoul, Korea. Received: May 26, 2009 Revised: September 4, 2009 Accepted: September 7, 2009 Corresponding author: Dr. June Myung Kim, Department of Internal Medicine, Yonsei University College of Medicine, 250 Seongsan-ro, Seoul 120-752, Korea. Tel: 82-2-2228-1946, Fax: 82-2-393-6884 E-mail: jmkim@yuhs.ac ∙ The authors have no financial conflicts of interest. © Copyright: Yonsei University College of Medicine 2011 This is an Open Access article distributed under the terms of the Creative Commons Attribution Non- Commercial License (http://creativecommons.org/ licenses/by-nc/3.0) which permits unrestricted non- commercial use, distribution, and reproduction in any medium, provided the original work is properly cited. Metallo-β-lactamase (MBL) production usually results in high-level resistance to most β-lactams, and a rapid spread of MBL producing major gram-negative patho- gens is a matter of particular concern worldwide. However, clinical data are scarce and most studies compared MBL producer (MP) with MBL non-producer (MNP) strains which included carbapenem susceptible isolates. Therefore, we collected clinical data of patients in whom imipenem-nonsusceptible Pseudomonas aerugi- nosa (PA) and Acinetobacter baumannii (AB) were isolated from sputum or urine, and investigated MBL production and the risk factors related with MBL acquisi- tion. The antimicrobial susceptibility patterns were also compared between MPs and imipenem-nonsusceptible MNPs (INMNP). Among the 176 imipenem-nonsus- ceptible isolates, 12 MPs (6.8%) were identified. There was no identifiable risk fac- tor that contributed to the acquisition of MPs when compared to INMNPs, and case-fatalities were not different between the two groups. The percentage of suscep- tible isolates was higher among MPs for piperacilin/tazobactam and fluoroquino- lones while that of ceftazidime was higher in INMNPs (p < 0.05). As regards to az- treonam, which has been known to be a uniquely stable β-lactam against MBLs, susceptibility was preserved in only two isolates (16.7%) among MPs, and was not higher than that of INMNPs (23.2%). In conclusion, the contribution of MBLs to imipenem non-susceptibility in PA/ABs isolated from sputum and urine was rela- tively limited, and there was no significant risk factor associated with acquisition of MPs compared with INMNPs. However, limited susceptibility to aztreonam im- plies that MPs may hold additional resistance mechanisms, such as extended spec- trum β-lactamases, AmpC β-lactamases, or other non-enzymatic mechanisms. Key Words: Metallo-β-lactamase, risk factor, resistance Acquired carbapenemases represent a major threat to the clinical utility of all Yonsei Med J http://www.eymj.org Volume 52 Number 2 March 2011 351