title: The characteristics of metallo-β-lactamase-producing gram-negative bacilli isolated from sputum and urine: a single center experience in Korea.
abstract: 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 pathogens 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 aeruginosa (PA) and Acinetobacter baumannii (AB) were isolated from sputum or urine, and investigated MBL production and the risk factors related with MBL acquisition. The antimicrobial susceptibility patterns were also compared between MPs and imipenem-nonsusceptible MNPs (INMNP). Among the 176 imipenem-nonsusceptible isolates, 12 MPs (6.8%) were identified. There was no identifiable risk factor that contributed to the acquisition of MPs when compared to INMNPs, and case-fatalities were not different between the two groups. The percentage of susceptible isolates was higher among MPs for piperacilin/tazobactam and fluoroquinolones while that of ceftazidime was higher in INMNPs (p < 0.05). As regards to aztreonam, 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 relatively limited, and there was no significant risk factor associated with acquisition of MPs compared with INMNPs. However, limited susceptibility to aztreonam implies that MPs may hold additional resistance mechanisms, such as extended spectrum β-lactamases, AmpC β-lactamases, or other non-enzymatic mechanisms.
authors.affiliation: AIDS Research Institute and Department of Internal Medicine, Yonsei University College of Medicine, Seoul, Korea.
authors.forename: Bum Sik
authors.initials: BS
authors.lastname: Chin
authors.forename: Sang Hoon
authors.initials: SH
authors.lastname: Han
authors.forename: Suk Hoon
authors.initials: SH
authors.lastname: Choi
authors.forename: Han Sung
authors.initials: HS
authors.lastname: Lee
authors.forename: Su Jin
authors.initials: SJ
authors.lastname: Jeong
authors.forename: Hee Kyung
authors.initials: HK
authors.lastname: Choi
authors.forename: Jun Yong
authors.initials: JY
authors.lastname: Choi
authors.forename: Young Goo
authors.initials: YG
authors.lastname: Song
authors.forename: Chang Ki
authors.initials: CK
authors.lastname: Kim
authors.forename: Dongeun
authors.initials: D
authors.lastname: Yong
authors.forename: Kyungwon
authors.initials: K
authors.lastname: Lee
authors.forename: June Myung
authors.initials: JM
authors.lastname: Kim
mesh_terms: D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D000900:Anti-Bacterial Agents / Q000494:pharmacology / Q000627:therapeutic use; D002648:Child; D002675:Child, Preschool; D016521:Electrophoresis, Gel, Pulsed-Field; D005260:Female; D006090:Gram-Negative Bacteria / Q000187:drug effects / Q000201:enzymology* / Q000302:isolation & purification; D016905:Gram-Negative Bacterial Infections / Q000188:drug therapy / Q000201:enzymology / Q000382:microbiology; D006801:Humans; D008297:Male; D008826:Microbial Sensitivity Tests; D008875:Middle Aged; D056910:Republic of Korea; D013183:Sputum / Q000382:microbiology*; D014556:Urine / Q000382:microbiology*; D018440:beta-Lactam Resistance; D001618:beta-Lactamases / Q000378:metabolism*
chemical_list: D000900:Anti-Bacterial Agents; D001618:beta-Lactamases