Moraxella is a genus of Gram-negative bacteria in the Moraxellaceae family. The organisms are short rods, coccobacilli or, as in the case of Moraxella catarrhalis, diplococci in morphology, with asaccharolytic, oxidase-positive and catalase-positive properties. Moraxella catarrhalis is the clinically most important species under this genus.
Roles in disease
The organisms are commensals of mucosal surfaces and sometimes give rise to opportunisitic infection
- Moraxella catarrhalis usually resides in respiratory tract, but can gain access to the lower respiratory tract in patients with chronic chest disease or compromised host defences, thus causing tracheobronchitis and pneumonia. It causes similar symptoms to Haemophilus influenzae, although it is much less virulent. Unlike Neisseria meningitidis, which is a morphologic cousin of Moraxella catarrhalis, it hardly ever causes bacteremia or meningitis.
- Moraxella lacunata is one of the causes of blepharoconjunctivitis in human.
- Moraxella bovis is the cause of Infectious Bovine Keratoconjunctivitis; known colloquially in the United Kingdom as 'New Forest Eye'. As a strict aerobe, M. bovis is confined to the cornea and conjunctiva, resulting in a progressive, non-self-limiting keratitis, ulceration and - ultimately - rupture of the cornea. The disease is relatively common, infecting cattle only. Treatment is via the use of either subconjunctival injection of a Tetracycline, or topical application of Cloxacillin, the former being more effective. The bacterium can be transmitted by flies, so fly control may be necessary on farms throughout the summer. Rupture of the eye is more serious, and requires immediate enucleation, though the procedure itself carries a good prognosis.