Staphylococcus aureus: characters associated with its pathogenicity and sensitivity to antibiotics.

A hundred staphylococcus strains recently isolated from hospital specimens of various kinds were first divided into two groups: mannitol-positive (90 strains) and mannitol-negative (10 strains). Their ability to produce protein A was then correlated with the presence of other metabolic and enzymatic characters typical of S.aureus. The results showed that satisfactory identification of S. aureus in clinical practice requires assessment of other more species-specific characters in addition to the mannitol fermentation, though this is useful as a preliminary screening measure. Evaluation of protein A production would seem as good or even better than evaluation of coagulase for this purpose. It was also found that the strains examined displayed an increased resistance to methicillin, particularly the part of non-aureus (mainly S.epidermidis) strains. Nearly all strains displayed resistance to the penicillins through the production of penicillinase.