Microbiology and Epidemiology

M. catarrhalis is an unencapsulated gram-negative diplococcus. Part of the normal flora of the upper airways, M. catarrhalis colonizes 33-100% of infants; the prevalence of colonization decreases steadily with age.

Clinical Manifestations

• M. catarrhalis causes 15-20% of cases of acute otitis media in children. Acute otitis media caused by M. catarrhalis or NTHi is clinically milder than cases caused by Streptococcus pneumoniae, with less fever and a lower frequency of an erythematous, bulging tympanic membrane.
• M. catarrhalis accounts for ∼20% of cases of acute bacterial sinusitis in children and for a smaller proportion in adults.
• In adults, M. catarrhalis is a common cause of exacerbations of COPD, accounting for ∼10% of cases.
• M. catarrhalispneumonia is uncommon, generally affecting elderly pts with underlying cardiopulmonary disease.

Diagnosis

Invasive procedures are needed to definitively identify the etiology of otitis media or sinusitis and generally are not performed. Isolation of M. catarrhalis from sputum samples from pts with COPD is suggestive, but not diagnostic, of M. catarrhalis as the cause.