Bacterial resistance monitoring of Salmonellas isolated from animals, national experience of surveillance schemes in the United Kingdom

Antimicrobial resistance has been monitored in salmonellas isolated from animals in England and Wales since 1970. The current trends are indicated by comparing the results for the years 1981, 1989 and 1990. Seventy-six per cent of all salmonella isolations are still sensitive to all 16 antimicrobials used for testing. Most antimicrobial resistance is encountered in bovine isolations of Salmonella typhimurium especially phage type DT204C. This phage type, which was initially resistant to at least seven antimicrobials, has however become more susceptible in recent years. Ninety-eight per cent of S. dublin strains from cattle are still sensitive to all the antimicrobials used for testing. Although the number of porcine salmonella isolations is small, many show antimicrobial resistance especially to tetracyclines. A large increase in the number of salmonellas isolated from poultry has occurred in recent years and 75% of these strains are sensitive to all the antibiotics used for testing. Although there has been a slight decrease in the percentage of S. enteritidis strains showing susceptibility 87% of isolations are still sensitive. The emergence of resistance to the newer antimicrobials trimethoprim, apramycin and fluorquinolones has been studied and data presented. The results are discussed with regards to the choice of techniques, bacteria monitored and future surveillance programmes in relation to the veterinary use of antimicrobials.