Prevalence of beta-lactamases among ampicillin-resistant Escherichia coli and Salmonella isolated from food animals in Denmark

Microb Drug Resist. 2004 Winter;10(4):334-40. doi: 10.1089/mdr.2004.10.334.

Abstract

The genetic background for beta-lactamase-mediated resistance to beta-lactam antibiotics was examined by PCR and sequencing in 160 ampicillin-resistant isolates (109 Escherichia coli and 51 Salmonella) obtained from healthy and diseased food animals in Denmark. Sequencing revealed three different variants of bla (TEM-1), of which bla (TEM-1b) was the most frequently detected (80 E. coli and 47 Salmonella), followed by bla (TEM-1a) (eight E. coli, one Salmonella) and bla (TEM-1c) (seven E. coli). A few isolates were found to express OXA, TEM-30, or PSE beta-lactamases. Mutations in the ampC promoter leading to increased production of the AmpC beta-lactamase were demonstrated in 11 cefoxitin-resistant or intermediate E. coli isolates. Nine of these isolates did not contain any bla (TEM) genes, whereas the remaining two did. No genes encoding SHV or extended-spectrum beta-lactamases were detected. Two new variants of bla (TEM) were detected, which have been designated bla (TEM-127) and bla (TEM-128). In TEM-127, amino acid 158 is substituted from His to Asn, whereas a substitution from Asp to Glu is seen at amino acid 157 in TEM-128. According to MIC determinations, these novel enzymes do not possess activity against extended-spectrum beta-lactams.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Ampicillin / pharmacology
  • Animals
  • Animals, Domestic*
  • Cattle
  • Chickens
  • Escherichia coli / drug effects
  • Escherichia coli / enzymology*
  • Escherichia coli / genetics
  • Escherichia coli Infections / microbiology
  • Meat Products / microbiology*
  • Microbial Sensitivity Tests
  • Prevalence
  • Salmonella / drug effects
  • Salmonella / enzymology*
  • Salmonella / genetics
  • Salmonella Infections / microbiology
  • Swine
  • beta-Lactam Resistance
  • beta-Lactamases / genetics*
  • beta-Lactamases / metabolism
  • beta-Lactams / pharmacology

Substances

  • beta-Lactams
  • Ampicillin
  • beta-Lactamases