The taxonomic definitions of these genera are still inconclusive. Bergey's Manual of Systematic Bacteriology groups both under the family Moraxella-ceae. These bacteria are short, rounded rods, often coccoid, sometimes also diplococcoid. Their natural habitat is either human mucosa (Moraxella) or the natural environment (Acinetobacter).
■ Moraxella. The genus comprises two medically important species:
— Moraxella catarrhalis. Component of the normal flora of the upper respiratory tract. May be responsible for: pneumonia, acute exacerbation of chronic bronchitis, otitis media (up to 20% in children), and sinusitis. About 90 % of all strains produce one of the so-called BRO penicillinases, so that therapy with a penicillinase-stable betalactam antibiotic is indicated.
— Moraxella lacunata. Formerly Diplobacterium Morax-Axenfeld. Can cause conjunctivitis and keratitis. The reason why this organism is now rarely found as a pathogen in these eye infections is unknown.
■ Acinetobacter. In immunodeficient persons, A. baumannii, A. calcoaceti-cus, and other species can cause nosocomial infections (urinary tract infections, pneumonias, wound infections, sepsis). Clinical strains of these species often show multiresistance to antibiotics, so that treatment of these infections may prove difficult.
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