The resistance to antimicrobial agents of Staphylococcus aureus isolated from the bovine udder

Isolates of Staphylococcus aureus (total 1657) from bovine mastitis were collected from 13 laboratories throughout Australia from 1974 to 1979. They were tested for resistance to antimicrobial agents using an agar dilution method. Resistance shown was mainly to penicillin and streptomycin. Occasional strains were resistant to neomycin, lincomycin, erythromycin, tetracycline, chloramphenicol and furazolidone but multiple resistance was rare. No strain showed resistance to methicillin. Resistance to penicillin declined from 35% in 1974-75 to 7.1% in 1979. Most strains (1395) were retested to allow induction of penicillinase; 62% produced the enzyme.