Phage typing of Staphylococcus aureus

Abstract

Phage adsorption by resistant staphylococci was studied.Staphylococcal cultures previously allowed to adsorb phage to which they were resistant remained as sensitive to their appropriate phages as normal cultures of the same strains.When pooled related and unrelated phages were incubated with their propagating strains, the results resembled those obtained when these phages were incubated separately with the same strains.The lytic effects of thirty-two phages at test dilutions were tested singly and when pooled into five mixtures. All the phage-propagating strains and over 500 strains received for typing were tested. The results were in agreement.Thirty-two phages at their test dilution in nutrient broth remained stable, whether pooled or not, at 0 to + 5° C. for various times. Briefly summarized, serological group A phages were stable for at least 1 month, and group B phages were stable for only 2–3 weeks.Broth cultures of staphylococci incubated for 18 hr. at 30° C. were as phage-sensitive as the same cultures when left at room temperature for 24 hr.A new method of phage typing staphylococci by means of phage pools, as satisfactory as the standard method, and less laborious, is described.