Branhamella (Moraxella) catarrhalis is a gram-negative diplococcus that is morphologically indistinguishable from Neisseria.1 In 1970, M catarrhalis was transferred to a new genus, Branhamella, and separated from other species of Moraxella. Branhamella catarrhalis principally colonizes the upper respiratory tract. It is a common cause of otitis media and sinusitis and has become an increasingly important pathogen for lower respiratory tract infections in patients with chronic obstructive pul monary disease. Approximately 75% of strains of B catarrhalis produce β-lactamase and are therefore resistant to penicillin and penicillin derivatives. Branhamella catarrhalis may also exhibit resistance to vancomycin or clindamycin. It remains sensitive to most other oral or intravenous antibiotics.
The related Moraxella organisms are principally associated with external eye disease, especially corneal ulcers in debilitated patients. Outbreaks of Moraxella conjunctivitis in children have also been reported. To our knowledge, Moraxella species have been reported as the etiologic agent in three cases
Bergren RL, Tasman WS, Wallace RT, Katz LJ. Branhamella (Moraxella) catarrhalis Endophthalmitis. Arch Ophthalmol. 1993;111(9):1169-1170. doi:10.1001/archopht.1993.01090090021009