title: Bloodstream infections caused by IMP-8-producing Enterobacteriaceae isolates: the need for clinical laboratory detection of metallo-β-lactamases?
abstract: A retrospective study was conducted at a Taiwanese medical center to characterize bloodstream infections caused by IMP-8 metallo-β-lactamase (MBL)-producing Enterobacteriaceae isolates and to assess the need for laboratory detection of IMP producers. We analyzed 37 patients infected with IMP-8 producers (two Escherichia coli, nine Klebsiella pneumoniae, 25 Enterobacter cloacae, and one Citrobacter freundii) and 107 patients infected with non-IMP-8 producers (eight E. coli, 26 K. pneumoniae, 70 E. cloacae, and three C. freundii) that were interpreted as carbapenem-nonsusceptible based on the updated Clinical and Laboratory Standards Institute (CLSI) 2010 guidelines. Only 18 (48.6 %) of the IMP-8 producers were regarded as potential carbapenemase producers based on the CLSI 2012 guidelines. The production of extended-spectrum β-lactamases (ESBLs) was more common in the MBL group (73.0 %) than in the non-MBL group (41.1 %). There were no significant differences in carbapenem susceptibilities, clinical characteristics, carbapenem use for empirical and definitive treatment, and mortality rates between the two groups. Eighteen IMP-8 producers could be deemed as resistant to all carbapenems [minimum inhibitory concentration (MIC) of any carbapenem ≥2 μg/mL]; patients with these isolates had a lower, but non-significant, 28-day mortality rate (27.8 %) than patients infected with non-MBL producers having similar carbapenem MICs (39.0 %) (p = 0.41). A multivariate analysis revealed severity of acute illness as the single independent variable associated with both 7-day and 28-day mortality rates (p < 0.01) for infections caused by Enterobacteriaceae with decreased carbapenem susceptibilities. Our findings suggest that the clinical detection of IMP-producing Enterobacteriaceae is not required even when the "old" CLSI criteria are used.
authors.affiliation: Department of Pathology, National Cheng Kung University Hospital, College of Medicine, National Cheng Kung University, 138 Sheng-Li Road, Tainan 70428, Taiwan. jingjou@mail.ncku.edu.tw
authors.forename: J J
authors.initials: JJ
authors.lastname: Yan
authors.forename: N Y
authors.initials: NY
authors.lastname: Lee
authors.forename: H M
authors.initials: HM
authors.lastname: Chen
authors.forename: M C
authors.initials: MC
authors.lastname: Wang
authors.forename: W C
authors.initials: WC
authors.lastname: Ko
authors.forename: L H
authors.initials: LH
authors.lastname: Tsai
authors.forename: J J
authors.initials: JJ
authors.lastname: Wu
mesh_terms: D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D000900:Anti-Bacterial Agents / Q000494:pharmacology; D016470:Bacteremia / Q000453:epidemiology* / Q000382:microbiology / Q000473:pathology; D015780:Carbapenems / Q000494:pharmacology; D004755:Enterobacteriaceae / Q000187:drug effects / Q000201:enzymology* / Q000302:isolation & purification; D004756:Enterobacteriaceae Infections / Q000453:epidemiology* / Q000382:microbiology / Q000473:pathology; D005260:Female; D006801:Humans; D008297:Male; D008826:Microbial Sensitivity Tests; D008875:Middle Aged; D012189:Retrospective Studies; D013624:Taiwan / Q000453:epidemiology; D001618:beta-Lactamases / Q000378:metabolism*
chemical_list: D000900:Anti-Bacterial Agents; D015780:Carbapenems; C436760:IMP-8 enzyme; D001618:beta-Lactamases