Bacteriophage typing of Staphylococcus aureus strains isolated from Bloemfontein dairy herds.

Bacteriophage typing was performed on 88 coagulase positive Staphylococcus aureus strains isolated during a survey of subclinical mastitis in Bloemfontein dairy herds. Phage typing was performed using two basic international phage typing sets, i.e. the human isolate phage set (HPS) and the bovine isolate phage set (BPS). The results clearly indicated that the BPS could be successfully applied for the phage typing of bovine mastitis S. aureus strains. The majority of the strains was typed as BPS phage group IV (78,4%) and HPS group III (47,7%). The high prevalence of BPS group IV strains is in agreement with other studies. The prevalence of non-typable strains was 3,4% for BPS and 28,4% for HPS. Phages 102, 117, 107, 81, 47, and 6 had high lytic activity. BPS group IV patterns (102/107/117 and 102/117) dominated. The incidence of unique phage patterns was 12,5% for BPS and 26,0% for HPS. A relatively high proportion (71,3%) of the strains was typable with the HPS. As these strains were of possible human origin it indicated the possibility of mutual human-animal transfer of the pathogens. No relationship could be found between phage groups on the one hand and multiple antibiotic resistance on the other, and no phage groups dominated within herds.