A double-blind comparison of the effects of cefaclor and amoxycillin on respiratory tract and oropharyngeal flora and clinical response in acute exacerbations of bronchitis.

Fifty-one patients admitted to hospital with severe exacerbations of chronic bronchitis entered a double-blind trial of treatment with cefaclor (500 mg tds) compared with amoxycillin (500 mg tds) for 7 days. Twenty-six patients received cefaclor and 25 amoxycillin. Sputum and throat swabs were collected on admission, after 7 days of therapy and at outpatient follow-up, 3 weeks after treatment had finished. Clinical status and spirometry were assessed on admission and at the third, seventh and 28th day. There was no significant difference between the two regimes for clinical outcome, spirometry or numbers of infecting pathogens. Opportunistic colonization with resistant Gram-negative organisms and Candida species was highly prevalent on admission (56%) in both groups, perhaps because of previous antibiotic administration and general debility of the majority of patients. The high prevalence of opportunistic colonizing organisms persisted at follow-up (48%) with a significant excess of new organisms (Enterobacter cloacae, Klebsiella species and Candida species) present in sputum in the amoxycillin-treated patients. Cefaclor may be less damaging to normal flora than amoxycillin with a consequently reduced risk of colonization and superinfection of the respiratory tract with resistant Gram-negative organisms and yeasts.