Studies on the Incidence of Coagulase-Positive Staphylococci in a Normal Unconfined Population

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Abstract
Some of the factors involved in the distribution of coagulase-positive staphylococci in a normal, unconfined population were investigated. The influence of race, sex, age and season of the year on the nasal carriage of S. aureus was determined. The following relationships were noted: (a) Thirty-seven per cent of the 147 white females and 38% of the 271 white males were carriers. (b) Twenty per cent of the 87 Negro females and 10% of the 72 Negro males carried coagulase-positive staphylococci. (c) Statistical evaluation of the data indicated that nasal carriage of S. aureus was associated with race. (d) No significant relationship could be shown between carrier rate and sex, age, or season. A comparison of several isolating media routinely used for the primary isolation of S. aureus was made prior to the initiation of the nasal carrier rate studies. (a) Rabbit-blood agar was inadequate as a differential isolating medium. There was poor correlation between hemolysis on this agar and coagulase production. (b) Sheep-blood agar was an efficient medium for primary isolation of coagulase-positive staphylococci. A high correlation existed between alpha hemolysis on sheep-blood agar and the production of coagulase.