Microbiologic and therapeutic aspects of Staphylococcus aureus in cystic fibrosis patients.

Staphylococcus aureus was the most frequent (28.8%) gram-positive organism in 149 cystic fibrosis patients. Next to Pseudomonas aeruginosa, S. aureus was the most persistent bacterial pathogen as well. Persistence was not correlated to the age or sex of our patients. Colonization by S. aureus was not prevented completely by oral antibiotics like cotrimoxazole or oral cephalosporins. Persisting staphylococci were less susceptible to the antibiotic substances used than strains detectable only sporadically. Increase of sputum concentrations of P. aeruginosa was observed in episodes of treatment with purely antistaphylococcal compounds. Improvement of effectiveness of antibacterial therapy may be achievable by antibiotics more active against staphylococci, active both against staphylococci and P. aeruginosa, or adequate drug combinations.