LONG-TERM PERSISTENCE OF CIPROFLOXACIN-RESISTANT HAEMOPHILUS-INFLUENZAE IN PATIENTS WITH CYSTIC-FIBROSIS

Ciprofloxacin has been a major advance in the treatment of chronic res piratory infections. Three patients with cystic fibrosis and colonized by 5 nontypeable Haemophilus influenzae strains exhibiting low- (MIG, 2 mu g/mL) and high-level ciprofloxacin resistance (MICs, 16-32 mu g/ mL) are described, The patients had received several courses of ciprof loxacin. These MICs represent a decrease in ciprofloxacin susceptibili ty of 200-3200 times. Molecular epidemiologic methods demonstrated tha t 2 patients were chronically colonized by their own ciprofloxacin-res istant strains for greater than or equal to 15-17 months. Three strain s showed simultaneous resistance to ampicillin and chloramphenicol by enzyme inactivation, and 2 had ampicillin resistance without beta-lact amase activity. These data suggest that the emergence and long-term pe rsistence of ciprofloxacin-resistant H. influenzae in patients with cy stic fibrosis can be a consequence of antibiotic treatment.