Overview

Moraxellaceae is a family of bacteria placed within the class Gammaproteobacteria. Members of this family are widely distributed in nature and include species found in soil, water, animals and humans. Some members are harmless environmental organisms while others are associated with disease.

Characteristics

Species in Moraxellaceae are typically gram-negative, non–spore-forming and range from short rods to coccobacilli. They are generally aerobic, though metabolic traits vary by genus. Oxidase activity and other biochemical tests distinguish genera: for example, Moraxella species tend to be oxidase-positive while Acinetobacter species are often oxidase-negative.

Genera and ecology

Common genera include Moraxella, Acinetobacter and Psychrobacter. These bacteria occupy diverse habitats—some are adapted to cold or marine environments (Psychrobacter), others persist on human skin and mucous membranes, and several tolerate desiccation and survive on surfaces. Environmental species can participate in nutrient cycling and biodegradation.

Medical and veterinary importance

Certain members are notable pathogens. Moraxella catarrhalis is associated with respiratory infections, otitis media in children and can aggravate chronic lung disease and COPD exacerbations. In animals, Moraxella bovis causes infectious bovine keratoconjunctivitis (pinkeye) in cattle. The genus Acinetobacter includes opportunistic hospital-associated species, some of which exhibit multi-drug resistance and cause wound, bloodstream and ventilator-associated infections.

Identification, taxonomy and relevance

Diagnostics combine phenotypic tests and molecular methods (such as 16S rRNA sequencing) to resolve genera and species. Taxonomy has shifted as molecular data clarified relationships. Beyond clinical concerns, some Moraxellaceae are studied for biodegradation and biotechnological applications, and their presence on surfaces and in cold environments makes them relevant to food safety and ecology.

  • Key distinctions: oxidase reaction, habitat and genetic markers help separate genera.
  • Clinical note: infection control and appropriate antibiotic selection are important where Acinetobacter and Moraxella cause disease.