Acinetobacter

Acinetobacter is a genus of Gram-negative, nonmotile, oxidase-negative, catalase-positive, nonfermenting bacteria in the family Moraxellaceae. They are obligate aerobes and typically appear as short coccobacilli in clinical specimens. The organisms are widespread in soil, water, and various hospital and community environments and can colonize human skin and mucous membranes.

Clinical relevance: Acinetobacter species are opportunistic pathogens, with Acinetobacter baumannii the most notable due to hospital-associated outbreaks and multidrug resistance. Infections include pneumonia (often ventilator-associated), bloodstream infections, wound and burn infections, urinary tract infections, and meningitis. They can persist on dry surfaces for extended periods and spread via contaminated equipment and hands of healthcare workers.

Identification and treatment: Laboratory identification uses Gram staining, oxidase testing (negative), nonfermentative metabolism, and culture; MALDI-TOF can aid species-level ID. The A. baumannii complex is frequently implicated in outbreaks. Antibiotic resistance is common; MDR and XDR strains limit treatment options. Therapies may include combinations guided by susceptibility testing, with options such as sulbactam-containing regimens, polymyxins (colistin), and tigecycline, depending on regional resistance patterns. Strict infection control is essential.

Taxonomy: The genus belongs to the family Moraxellaceae, order Moraxellales, class Gammaproteobacteria. It encompasses several medically important species, including A. baumannii, A. nosocomialis, A. pittii, and A. calcoaceticus.