Sensitivity of staphylococci from farm animals to antibacterial agents used for growth promotion and therapy. A ten year study.

The following results were obtained during the period of 1970 to 1979-1980 in a study of 1040 Staphylococcus aureus strains in Belgium from cattle, poultry and pigs and 138 Staphylococcus hyicus strains from pigs, using the agar dilution technique and different penicillinase test methods: -- The incidence of penicillinase-positive strains increased in bovine and porcine S. aureus strains but decreased in poultry strains. From 1974 on more than 75% of S. aureus strains from cow udders produced penicillinase. -- The numbers of tetracycline-resistant strains steadily decreased during the period under investigation. -- Strains resistant to the macrolides and lincomycin were most frequent among S. hyicus and S. aureus strains from pigs isolated in 1973-1975. They were less numerous in 1979-1980. The inducible type of macrolide-resistance was found only among strains from poultry and cattle. In 1979-1980 strains resistant to lincomycin but susceptible to macrolide-antibiotics were detected. -- Two types of sensitivity to bacitracin were discovered: highly sensitive strains were frequent in cattle and rare in poultry. Intermediately sensitive strains dominated in poultry and pigs. These two groups of strains belonged to distinct chemotypes. Only one poultry strain was highly resistant to bacitracin. -- Number of neomycin-, sulphonamide- and chloramphenicol-resistant strains and strains resistant to the penicillinase-stable penicillins and cephalosporins were low and did not increase. -- Novobiocin resistance was only found among strains from broiler breeders and broilers. -- All strains tested were sensitive to the nitrofurans and related compounds (furazolidone, nitrovin), flavomycin, carbadox, trimethoprim, rifamycin and the virginiamycin combination.