Staphylococci on the skin of pigs: isolates from two farms with different antibiotic policies.

Staphylococci isolated from pigs on two farms were identified and their antibiotic resistance and plasmid profiles were examined. A highly resistant Staphylococcus hyicus was epidemic on one of the farms which was also that at which antibiotic-containing feedstuffs were used most often. Staphylococci from this farm were more often resistant to two or more antibiotics than were the strains from the other farm. The many plasmids present in these staphylococci prevented the determination of the genetic nature of the antibiotic resistance.