Heat treatment to increase phage typability of Staphylococcus aureus

Heat treatment was used to reduce the number of Staphylococcus aureus strains that were not typable with the basic set of phages. All strains were phage typed according to the standard method after growth in broth at 37 degrees C or 48 degrees C. Forty-eight of 72 nontypable strains could be phage typed after heat treatment of the bacterial cultures. The page lysability increased with the higher incubation temperature of the broth, but the mean variability in the phage pattern of a strain was not significantly affected. The phage typing results of strains sampled over a period of several months were in accordance with the epidemiology, suggesting that phage typing after incubation at 48 degrees C is a stable and useful epidemiological tool.