Beta-lactamase patterns and beta-lactam/clavulanic acid resistance in Escherichia coli isolated from fecal samples from healthy volunteers


Gulay Z., Bicmen M., Amyes S., Yulug N.

JOURNAL OF CHEMOTHERAPY, vol.12, no.3, pp.208-215, 2000 (SCI-Expanded) identifier identifier identifier

  • Publication Type: Article / Article
  • Volume: 12 Issue: 3
  • Publication Date: 2000
  • Doi Number: 10.1179/joc.2000.12.3.208
  • Journal Name: JOURNAL OF CHEMOTHERAPY
  • Journal Indexes: Science Citation Index Expanded (SCI-EXPANDED), Scopus
  • Page Numbers: pp.208-215
  • Keywords: Escherichia coli, clavulanic acid, commensal flora, resistance, beta-lactamase, ampicillin
  • Dokuz Eylül University Affiliated: No

Abstract

Fecal specimens from 50 healthy volunteers living in Izmir, Turkey, were examined for the presence of beta-lactamase producing Escherichia coli by selection on agar plates containing ampicillin (10 mg/L). Thirty-nine (78%) of the strains were ampicillin-resistant and ampicillin MIC50 values for these isolates were greater than or equal to 1024 mu g/ml (range 32- greater than or equal to 1024 mu g/ml). Ampicillin MIC values remained above 64 mu g/ml in 16 (41%) strains despite addition of clavulanic acid (2 mg/L). Beta-lactamase production of the clavulanate-resistant strains was further investigated by analytical isoelectric focusing (pI). Enzymes with pIs of 5.4, 5.6, 7.4, 7.6 and >8.5 were detected. Sixty-nine percent of the isolates produced a pI 5.4 enzyme that cofocused with TEM-1. Beta-lactamase assays revealed that hyperproduction of these enzymes was the predominant mechanism for clavulanate resistance. Twelve (75%) of the isolates were able to transfer their ampicillin resistance. The ampicillin and ampicillin plus clavulanic acid MIC values of all transconjugants were above 256 mu g/ml. Transferable ampicillin resistance was associated with resistance to other antibacterials at the following frequencies: tetracycline 92%, trimethoprim 83%, streptomycin 50%, gentamicin 25%, and chloramphenicol 8%,