A Survey of Drug Resistance in Salmonellae Isolated from Animals in England and Wales During 1973 and 1974

Resistance to eight antibacterial drugs was tested in 5905 salmonella strains isolated from animals and their environment during 1973 and 1974. Twenty-six patterns of resistance were detected in 1973 and 23 patterns in 1974. While only 7·0% of the strains examined during 1973 were sensitive to all drugs tested, this figure rose to 20·7% of strains isolated during 1974. All the strains examined were sensitive to trimethoprim/sulphamethoxazole. During 1973 the percentages of strains resistant to streptomycin (10μg), compound sulphonamide (50μg), Chlortetracycline (10μg), neomycin (10μg), ampicillin (10μg), furazolidone (15μg) and chloramphenicol (10μg) were 75·9%, 66·2%, 5·0%, 1·3%, 0·6%, 1·1% and 0·3%, respectively. The corresponding figures for strains isolated during 1974 were 48·4%, 63·8%, 4·5%, 1·7%, 0·7%, 0·6% and 0·1%, respectively. Randomly selected strains were additionally tested for their sensitivity to streptomycin and sulphathiazole at higher concentrations using both the diffusion and dilution methods. Of a total of 796 strains examined 88 (11·1%) showed resistance to streptomycin at 25μg concentration and 92 (12·3%) of 749 strains showed resistance to sulphathiazole at the higher concentration.