Hospital infections caused by a group of recently recognized strains of Staphylococcus aureus.

A survey was made of the phage-types of staphylococci responsible for cross-infection in a large veterans' hospital between 1961 and 1964. An earlier survey had shown that in 1959 most of the infections were caused by staphylocci of the "80/81/82" group. In 1961 a new group of staphylococci were first recognized and provisionally designated as "Atypical Group III" strains; these were non-typable by the usual typing phages but showed inhibition patterns with some of the Group III phages. The "Atypical Group III" staphylococci all showed one or other of four patterns of multiple antibiotic resistance. By 1963 these resistant "Atypical Group III" staphylococci had become more frequent than "80/81/82" strains as causative agents of cross-infection, although both groups have continued to cause infections in the hospital. "Atypical Group III" strains mainly infected surgical wounds and skin ulcers, whereas "80/81/82" strains commonly produced primary skin sepsis, such as boils.