title: Clinical laboratory detection of AmpC β-lactamase: does it affect patient outcome?
abstract: Plasmid-mediated AmpC-producing Escherichia coli and Klebsiella pneumoniae have been associated with poor clinical outcomes, but they are not readily identified in hospital microbiology laboratories. We tested 753 gram-negative bloodstream isolates for AmpC by using the EDTA disk test and the modified Hodge test (n = 172) and the modified Hodge test alone (n = 581). The 30-day mortality for the AmpC group was 9% (2/23) and was 6% (3/51) for the control group. The clinical response was similar: afebrile on day 2 (AmpC group, 16/23 [70%]; control group, 32/45 [71%]) and on day 4 (AmpC group, 19/22 [86%]; control group, 37/44 [84%]). Patients with isolates in the AmpC group were more likely to be in an intensive care unit at the time of the positive blood culture (P = .01) and more likely to be intubated (P = .05) than patients with isolates in the control group. Effective antibiotic treatment within the first 48 hours was given to 47 (92%) of 51 patients with isolates in the control group but to only 14 (61%) of 23 patients with isolates in the AmpC group (P = .001). The modified Hodge test and the EDTA disk test did not identify patients at risk for a poor outcome from AmpC-producing bacterial infections.
authors.affiliation: Dept of Pathology, Immunology, and Laboratory Medicine, University of Florida, College of Medicine, Gainesville, 32601-0275, USA.
authors.forename: Kenneth H
authors.initials: KH
authors.lastname: Rand
authors.forename: Bradley
authors.initials: B
authors.lastname: Turner
authors.forename: Hilary
authors.initials: H
authors.lastname: Seifert
authors.forename: Christine
authors.initials: C
authors.lastname: Hansen
authors.forename: Judith A
authors.initials: JA
authors.lastname: Johnson
authors.forename: Andrea
authors.initials: A
authors.lastname: Zimmer
mesh_terms: D000328:Adult; D016470:Bacteremia / Q000188:drug therapy* / Q000382:microbiology / Q000401:mortality; D001426:Bacterial Proteins / Q000378:metabolism*; D001831:Body Temperature / Q000187:drug effects; D024881:Drug Resistance, Bacterial / Q000187:drug effects; D004755:Enterobacteriaceae / Q000187:drug effects / Q000201:enzymology / Q000302:isolation & purification*; D004756:Enterobacteriaceae Infections / Q000175:diagnosis* / Q000382:microbiology / Q000401:mortality; D005260:Female; D005431:Florida / Q000453:epidemiology; D006801:Humans; D008297:Male; D008826:Microbial Sensitivity Tests; D008875:Middle Aged; D010957:Plasmids; D015996:Survival Rate; D016896:Treatment Outcome; D001618:beta-Lactamases / Q000378:metabolism*
chemical_list: D001426:Bacterial Proteins; C048795:AmpC beta-lactamases; D001618:beta-Lactamases