Significance of isolation of Moraxella catarrhalis in routine cultures from the respiratory tract in adults: antibody response studied in a whole cell EIA.

The significance of the isolation of Moraxella catarrhalis from sputum or nasopharynx was studied in patients treated at an infectious disease clinic. A whole-cell enzyme immunoassay was used to detect a specific antibody response to M. catarrhalis during infection. In all, 27 patients with respiratory tract infections and 4 with other infections were studied. Titre rises were recorded in 11/23 patients with lower respiratory tract infections, whereas patients with common cold or infections elsewhere all had negative serology. In patients with acute bronchitis, 7/10 patients responded with a significant titre rise. Patients with a low titre in their acute serum sample were those who responded with a titre increase during infection. The findings indicate that isolation of M. catarrhalis from sputa and nasopharyngeal samples in adults is of value for the etiological diagnosis of acute bronchitis and other lower respiratory tract infections, and is therefore important for the choice of drug for treatment, as many isolates are resistant to beta-lactam antibiotics.