Acinetobacter

Abstract

Found in the family Neisseriaceae, the genus Acinetobacter is large and contains many species formerly classified as Mima, Herellea, Moraxella, Bacterium, Achromobacter, and even Pseudomonas. Currently, only Acinetobacter calcoaceticus is recognized in Bergey's Manual. The phenotypic variability of this species, A. calcoaceticus, is explained on the basis of four biotypes. The biotypes are classed according to their hemolytic activity, production of gelatinase, ability to grow on Salmonella-Shigella (SS) agar, and production of acid from glucose. The two most clinically important and frequently encountered biotypes are A. calcoaceticus var. anitratus and A. calcoaceticus var. lwoffi. The other biotypes are A. calcoaceticus var. haemolyticus and A. calcoaceticus var. alcaligenes. Although they are not very virulent organisms, infections due to Acinetobacter species have been associated with a wide variety of nosocomial infections. Most infections involve patients with compromised host defenses. Acinetobacter has been associated with a variety of diseases including septicemia, with indwelling intravenous catheters as the suspected portal of entry; bacteriuria, usually associated with the presence of an indwelling bladder catheter; and pneumonias affecting those severely debilitated individuals who have undergone major surgery or trauma. Respiratory support equipment has been found to serve as a source or reservoir for these organisms. Most nosocomial colonizations and infections due to A. calcoaceticus are due to the anitratus variety.