Moraxella catarrhalis is a gram-negative, aerobic, oxidase-positive diplococcus, which may both colonise and cause respiratory tract-associated infection in humans.
Clinically, these bacteria are known to cause bronchitis, sinusitis, laryngitis and otitis media. Elderly patients and long-term heavy smokers with chronic pulmonary disease should be aware that M. catarrhalis is associated with bronchopneumonia, as well as exacerbations of existing chronic obstructive pulmonary disease (COPD).
Treatment options include antibiotic therapy or a so-called " watchful waiting" approach. The great majority of clinical isolates of this organism produce Beta-lactamases and are resistant to penicillin, with some suggestion of trimethoprim resistance in certain regions of the world. Fortunately, infections due to M. catarrhalis may be treated with most other types of antibiotics, including erythromycin, ciprofloxacin and gentamicin.
The peak rate of colonisation by M. catarrhalis appears to occur at approximately 2 years of age, with a striking difference in colonisation rates between children and adults (very high to very low).
Current research priorities involve trying to find a suitable vaccine for this genotypically diverse organism, as well as determining factors involved with virulence e.g. complement resistance.
Reference
Murray, P., Rosenthal, K., and Pfaller, M. (2005) Medical Microbiology Pg. 365.
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