Moraxella catarrhalis respiratory infection in adults.

Moraxella catarrhalis (MC) is an upper respiratory tract commensal which may also be pathogenic. In this report we examined the clinical features, microbiology and therapeutic response in 30 consecutive adult patients with pneumonia who had MC isolated in the sputum. The mean age was 66 years with an equal sex ratio. Most patients gave a history of cigarette smoking (77%) and had underlying pulmonary diseases (73%). Dyspnea and productive cough were the most common complaints (87%). Fever was a manifestation in 60% of patients. Chest X-ray features of pneumonia were noted in 78% of patients while leucocytosis (> 11,000/mm3) was evident in 70%. While all isolates were susceptible to tetracycline, 70% were resistant to penicillin/ampicillin by in-vitro testing. Three patients died, two from their underlying illnesses and one from myocardial infarct. We believe that MC isolated in sputum cultures from symptomatic adults with underlying respiratory diseases should be treated as a pathogen. The short term prognosis is good.