Antimicrobial susceptibility of enterococci recovered from commercial swine carcasses: effect of feed additives

Enterococcus faecium is an important nosocomial pathogen often displaying m ultiple antibiotic resistance. The increase in clinical isolates can be att ributed in part to hospital practices in antibiotic usage, but there is con cern that antibiotic-resistant strains might also originate in animals fed rations containing antibiotic growth promoters. Ingestion of meat from carc asses contaminated with faecal enterococci might then result in human colon ization or resistance gene transfer to human enterococci. Because there are few comparisons of bacteria isolated from matched animals that have, or ha ve not, been fed a diet containing antibiotic, two such groups of pig carca sses were sampled at a commercial abattoir. Fort!; isolates from each group of pigs were tested for their resistance to avilamycin and tylosin. Althou gh a modest number of pigs was examined, and the number of strains of E. fa ecium tested was small, there was no evidence that the feeding of a growth promoter caused selection of enterococci resistant to tylosin or avilamycin .