In vitro susceptibility and resistance of animal staphylococci to macrolide antibiotics and related compounds.

Strains of Staphylococcus aureus isolated from poultry, pigs and cases of bovine mastitis and strains of S. hyicus isolated from pigs were examined for their susceptibility of the macrolides and other related antibiotics. The susceptibility of these strains to erythromycin, oleandomycin, tylosin, spiramycin, lincomycin, clindamycin, virginiamycin, and its components virginiamycin S and M, was tested by the quantitative plate dilution method. With S. aureus, 3 p. 100 of the bovine, 12 p. 100 of the avian and 53 p. 100 of porcine isolated were found to be resistant. With S. hyicus strains 76 p. 100 were found to be resistant. Most resistant strains showed the generalized constitutive macrolide-resistance type. Twelve p. 100 of the porcine S. aureus strains were resistant to the virginiamycin component M.