Objective: To study the microbiology of cystic fibrosis in our hospital for the period from 1985 to 1992.
Material and methods: The number of samples analyzed totalled 1,034, most of which were sputum and nasopharyngeal aspirates belonging to 113 patients (49 women and 64 men). The average age was 10 years (range: 15 days-33 years).
Results and discussion: Only 1.7% of the samples were negative. Normal flora were found in 10.8% and one or more potentially pathogenic microorganisms were found in the remaining 87.4%. Colonies were over 10(6) UFC/ml in size in 77.8% of the quantified cultures. The most frequently identified microorganisms in the population overall were P. aeruginosa (53.9%), S. aureus (30.3%) and H. influenzae (22.0%). In patients less than 12 months old, however, the most common isolations were of S. pneumoniae and B. catarrhalis; cultures from patients older than 16 years old most often yielded filiform fungi, mainly Aspergillus spp. We found no strains of Legionella spp. and P. cepacia was found in only 3 cases, in which the clinical outcome was good. In addition to the 3 most common organisms, we recorded several consecutive isolations of Proteus mirabilis, Xanthomonas maltophilia and Serratia marcescens in patients older than 11 years old; this finding suggests that given the improved survival of cystic fibrosis patients over the coming years and the antibiotic pressure placed on them, there may be slight changes in the bacterial ecology typical of this disease. No strain of S. aureus proved resistant to methicillin, but P. aeruginosa was shown to be resistant to gentamycin (58.2%) among the aminoglycosides and also to some of the beta-lactams considered to be effective, as follows: 25.2% to piperacillin, 22.6% to ceftazidime and even 19.8% to aztreonam. There was slight resistance of ciprofloxacin (6.3%).