Colonies of Moraxella catarrhalis on blood agar. Cultivation 24 hours, 37°C. Colonies are nonhemolytic.
Clinically, these bacteria are known to cause otitis media, bronchitis, sinusitis, and laryngitis. 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).
The peak rate of colonisation by M. catarrhalis appears to occur at approximately 2 years of age, with a striking difference in colonization rates between children and adults (very high to very low).
M. catarrhalis has recently been gaining attention as an emerging human pathogen. It has been identified as an important cause in branchopulmonary infection, causing infection through pulmonary aspiration in the upper pulmonary tract. Additionally, it causes bacterial pneumonia, especially in adults with a compromised immune system. It has also been known
to cause infective exacerbations in adults with chronic lung disease, and it is an important cause in acute sinusitis, maxillary sinusitis, bacteremia, meningitis, conjunctivitis, acute purulent irritation of chronic bronchitis, urethritis, septicemia (although this is rare), septic arthritis (which is also a rare occurrence), as well as acute laryngitis in adults and acute otitis media in children.