Identification of pathogenic staphylococci

Abstract

Morphological appearance, gelatin liquefaction and agglutination tests are not satisfactory criteria for the identification of pathogenic staphylococci. The coagulation of milk and lactose fermentation are not specific, showing positive results both for pathogenic strains as well as for the saprophytic ones. The mannitol test seems to be of value only in the negative case, as the staphylococci, which do not ferment this alcohol, are saprophytic. Of little value is the pigment production as a means of differentiating pathogenic from saprophytic strains of staphylococci, this pigmentation being a non-specific and variable biological feature. Animal inoculation is valuable provided susceptible animals showing no specific immunity and strains of staphylococci of increased virulence are used. These conditions make the application of the test difficult in routine work. Hemolysis of washed rabbit red blood-cells is of a high specificity and sensibility, being an excellent auxiliary method in the identification of the pathogenic staphylococci. The coagulation of plasma seems to be an ideal test for the identification of the pathogenic staphylococci because of its specificity, sensibility and the simplicity of its performance. Most authors who have studied this subject are of the same opinion. We intend to try this test in a larger scale until such a number of observations are obtained that will lead us to conclusions of the statistical standpoint of this subject.