THE DIFFERENTIATION OF PATHOGENIC STAPHYLOCOCCI FROM NON-PATHOGENIC TYPES

Abstract

Although numerous in vitro tests have been proposed for differ-entiating staphylococci on the basis of pathogenicity the subject is confusing to many workers. This paper describes attempts to determine the significance of certain tests. The following seem to have been the more common sources of confusion: (1) Most investigators have used a series of cultures which was too small for statistical analysis; (2) groups of cultures from different sources, or obtained at different times from the same type of source, may not yield the same proportion of positive results; (3) results based on the source of the strains usually ignore the possibility of error; (4) differences in technic, or in the in-terpretation of results, may be sufficient to cause two investigators to arrive at opposite conclusions; only infrequently has an author described tests, or their interpretation, with sufficient precision to permit others to duplicate them; (5) the dissociation of a strain, resulting in loss of one or more properties in some cells of the culture, causes it to become a mixture of variants with different pathogenic properties; and (6) pathogenic cultures de-generate or dissociate at different rates and in different ways, depending upon a number of poorly understood factors.