Clinical laboratory detection of AmpC β-lactamase: Does it affect patient outcome?

Kenneth H. Rand, Bradley Turner, Hilary Seifert, Christine Hansen, Judith A. Johnson, Andrea Zimmer

Research output: Contribution to journalArticlepeer-review

12 Scopus citations

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.

Original languageEnglish (US)
Pages (from-to)572-576
Number of pages5
JournalAmerican journal of clinical pathology
Volume135
Issue number4
DOIs
StatePublished - Apr 2011
Externally publishedYes

Keywords

  • AmpC β-lactamase
  • Bacteremia outcome
  • EDTA disk test
  • Modified Hodge test

ASJC Scopus subject areas

  • Pathology and Forensic Medicine

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