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June 14, 1965


JAMA. 1965;192(11):994. doi:10.1001/jama.1965.03080240064019

Bacteriophage typing of Staphylococcus aureus has provided much valuable information on the epidemiology of hospital-acquired infections. The procedure has been standard and used for three decades. Certain strains of S aureus possess intracellular agents, called bacteriophages, capable of lysing bacteria of other strains. Several distinct bacteriophages have been isolated, propagated in culture, and accepted for typing. They are known by numbers, letters, or a combination of numbers and letters, such as 80, 81, 3B, 3C. The procedure is to coat a culture plate with the "unknown" strain of S aureus, add a drop of each standard bacteriophage to different areas of the plate, and several hours later identify where inhibition has occurred. S aureus bacteriophage type 80/81, for example, is a strain inhibited by bacteriophages 80 and 81. Today there are 22 standard bacteriophages in diagnostic use, and most strains of S aureus can be identified by their susceptibility patterns