Antimicrobial resistant bacteria in red meat producing animals

Summary

Abattoir isolates of E.coli and Enterococcus spp obtained in the 2004 Microbial Survey of Australian Red Meat were examined for antimicrobial resistance.
221 E.coli isolates were tested for resistance to 17 antimicrobials and 300 Enterococcus isolates were tested for resistance to 8 antimicrobials.
A low level of anitmicrobial resistance was found for E.coli isolates.
The highest rate of resistance was to cephalothin at 3.9 per cent.
Expression of resistance to cephalothin by E.coli correlates poorly with susceptibility/resistance to other antimicrobials in the first generation cephalosporin class, suggesting that cephalothin may not be a reliable indicator of true resistance.
Enterococcus antimicrobial resistance was detected with the following frequencies:gentamicin - 1.3%levofloxacin - 1.3%quinupristin/dalfopristin - 5.0%streptomycin - 5.0%tetracycline - 7.0%vancomycin - 9.0%
No Enterococcus isolates were resistant to ampicillin or linezolid. 6 Enterococcus isolates from sheep carcases were resistant to both quinupristin/dalfopristin and tetracycline; such data may indicate ptotential selection pressure for resistance through the use of virginiamycin and tetracycline in sheep production systems.
The detection of E. faecalis and E. faecium  with resistance to vancomycin indicates potential that these isolates carry acquired resistance genes. Further clarification of the genetic basis for vancomycin resistance in these E. faecalis and E. faecium isolates will provide information that may indicate if identifiable antimicrobial selection plays a role in the presence of such isolates.