Bacteriophage 604: a marker phage for multi-resistant Staphylococcus aureus in Australia.

Of 28 multi-resistant isolates of Staphylococcus aureus collected during 1986 from hospitals in major cities around Australia, 27 were found to contain the same prophage (denoted phage 604). Hospital isolates carrying three or fewer resistance markers, and community isolates carrying one or no resistance markers, did not carry this prophage. Phage 604 does not confer antibiotic resistance on its lysogens, nor does it increase virulence in chick embryo assays. Phage 604 appears to be a correlate of antibiotic multi-resistance in S. aureus in Australia, and may provide a molecular marker for incipiently epidemic strains of this bacterium in Australian hospitals.