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.

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 against 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. 