Phage typing of nontypable isolates of Staphylococcus aureus using the new phages 94, 95, and 96 and the heat-shock treatment.

Of 2,144 isolates of Staphylococcus aureus (from human beings in New York State) received in the authors' laboratory during 1975, 992 (46.,%) were nontypable with the use of the international basic set of bacteriophages. These 2,144 isolates were retested with the use of the recently added phages 94, 95, and 96. Nearly 60% of the isolates were lysed with one or more of these three phages, including 64% of those previously nontypable, thus reducing the percentage of nontypables to 16.5%. One hundred randomly selected isolates that remained nontypable were heat-shocked and retested with the revised basic set of phages, which includes the three new phages. Forty-three isolates were typable with the use of this procedure; all but one of these produced the exact same phage pattern in at least three of five trials.