Minimal criteria for identification of Moraxella (Branhamella) catarrhalis.

A study was performed which aimed at testing the reliability of our routine diagnostic tests for identification of Moraxella (Branhamella) catarrhalis in clinical samples from the respiratory tract. A preliminary diagnosis of 122 isolates as Moraxella catarrhalis was obtained by using colony morphology and results of Gram stain and oxidase test as the sole diagnostic criteria. By using additional tests we could show that the preliminary diagnosis was incorrect for 21 isolates, which were classified as different Neisseria species. 20 of these were isolated from sputum samples. We propose that at least a test for DNA hydrolysis should be included in the routine procedure for identification of Moraxella catarrhalis in sputum.