A subdivision of strains of Staphylococcus aureus in the 94,96 complex by means of experimental phages

In order to facilitate epidemiological investigations a subdivision of Staphylococcus aureus strains belonging to the 94,96 complex by means of two experimental phages, 16 and 47A, was performed. These phages were selected from the nine experimental phages initially examined because they gave the greatest discrimination. On the basis of reactions with these two phages, 2199 isolates which reacted with phages 94 and 96, and 773 isolates which reacted with phage 96 alone, were each subdivided into two major and two minor groups. Strains with different phage patterns were in a few cases (2/64) isolated from the same deep body site in a patient, and lysogenisation experiments suggested that differences in phage patterns were determined by the presence of prophages. Strains with the phage patterns 94/96 and 96 were found to be unevenly distributed throughout Denmark. This regional distribution suggested that particular strains might predominate in some areas. The extended phage patterns with the experimental phages did not give any retrospectively useful epidemiological information. It is proposed that in future phages 16 and 47A be used for specific investigations into the sources and relatedness of strains involved in small incidents.