Staphylococcus aureus in cystic fibrosis: antibiotic sensitivity and phage types during the latest decade. Investigation of the occurrence of protein A and some other properties of recently isolated strains in relation to the occurrence of precipitating antibodies.

Abstract

During the recent decade, 1651 isolates of Staphylococcus aureus from 111 patients with cystic fibrosis have been tested for antibiotic sensitivity and half of the isolates have been phage typed. All the patients were followed in one clinic and the policy of antibiotic treatment was consistent during this period. The results show a dynamic situation where "epidemic" phage types during recent years have been gradually replaced by other types and, during the same period, the prevalence of strains resistant to more than one antibiotic decreased. Multiresistant strains including strains resistant to methicillin were infrequent in these patients. From 23 per cent of the patients, the same strains were repeatedly isolated for more than 1 year despite an apparently successful chemotherapy. Recently isolated strains were found to produce cellbound as well as extracellular protein A. Ninety-one per cent of the strains produced extracellular lipase and only 8 per cent were resistant to mercury chloride. Eighty-one per cent of the patients produced precipitating antibodies agains S. aureus as judged by crossed immunoelectrophoresis. The investigated properties of S. aureus were not significantly correlated with the occurrence of precipitating antibodies against these bacteria. The possible significance of protein A in the pathology of the respiratory tract infection is discussed.