Ciprofloxacin-resistant Haemophilus influenzae infection in a patient with chronic lung disease.

To report a case of ciprofloxacin-resistant Haemophilus influenzae infection in a patient with chronic lung disease who was exposed to multiple courses of antimicrobial therapy. The patient suffered recurrent pulmonary infections and developed bronchiectasis as a consequence of longstanding, severe, combined immunodeficiency disease. He had received ciprofloxacin on several occasions for treatment and prophylaxis of recurrent pulmonary infections. On a recent admission his usual H. influenzae isolate, which had been highly susceptible to ciprofloxacin (minimum inhibitory concentration [MIC] < or = 0.06 mg/L) on previous admissions, was resistant to ciprofloxacin and ofloxacin (MIC 8 and 16 mg/L, respectively). The patient responded to treatment with ceftizoxime and was discharged with oral cefixime, which was to be taken for a total of two weeks. Rare isolates of H. influenzae resistant to ofloxacin and lomefloxacin have been noted in Europe and Asia; however, none resistant to the fluoroquinolones have been previously reported in the US, and no resistance has been reported to ciprofloxacin. We believe that repetitive, cycling exposure to ciprofloxacin may have induced the resistance that developed in this patient's flora. Fluoroquinolones may be added to the list of drugs to which H. influenzae have become resistant. Only judicious use of these drugs will preserve their activity against important pathogens in community-acquired infections.