Moraxella catarrhalis

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Moraxella catarrhalis is a gram-negative, aerobic, oxidase-positive diplococcus that was described for the
first time in 1896. The organism has also been known as Micrococcus catarrhalis, Neisseria catarrhalis, and
Branhamella catarrhalis. For most of the 20th century, M catarrhalis was considered a saprophyte of the
upper respiratory tract with no significant pathogenic consequences.

Although the commensal status of M catarrhalis in the nasopharynx is still accepted, the organism is a
common cause of otitis media and sinusitis and an occasional cause of laryngitis. M catarrhalis causes
bronchitis or pneumonia in children and adults with underlying chronic lung disease and is occasionally a
cause of bacteremia or meningitis, especially in patients who are immunocompromised. Bacteremia can be
complicated by local infections such as osteomyelitis or septic arthritis. M catarrhalis is also associated with
nosocomial infections