A genus of strictly aerobic, oxidase −ve, catalase+ve,Gram-type-negative bacteria of the family MORAXELLACEAE (within the
gamma subdivision of PROTEOBACTERIA); the organisms occur e.g. in soil and water and may act as opportunist pathogens in man.
Cells: short rods, 0.9–1.6 × 1.5–2.5 micron,or coccobacilli (coccoid in stationary-phase cultures);cells often in pairs. Nonmotile, but may exhibit TWITCHING MOTILITY. Non-pigmented.
Metabolism is respiratory (oxidative), with oxygen as terminal electron acceptor; no growth occurs anaerobically, with or without nitrate.
Most strains can grow on a mineral salts medium containing an organic carbon source such as acetate,ethanol or lactate as the sole source of carbon andenergy; some can use amino acids (e.g. L-leucine,ornithine) and/or pentoses (e.g. Larabinose,D-xylose), and some are able to degrade e.g. benzoate,n-hexadecane and alicyclic compounds.
Acinetobacters appear to contain all the enzymes of the TCA CYCLE and the glyoxylate cycle. Many carbohydrates can be used. Most strains in the A. calcoaceticus–A. baumannii complex (and in certain other groups) can form acid from glucose (oxidatively), but many (e.g. most strains designated A. lwoffii ) cannot. The optimal growth temperature is typically 33–35°C.
GC%: ∼38–47. Type species: A. calcoaceticus.
The taxonomy of Acinetobacter is confused and unsatisfactory.Emended descriptions of the two species A. calcoaceticus and A. lwoffii, and proposals for four new species (A. baumannii, A. haemolyticus, A. johnsonii and A. junii ), were published in 1986 [IJSB (1986) 36 228–240]. Since then, a number of adjustments have been made to the taxonomic structure of the genus.
Acinetobacters have been isolated in a number of hospitalassociated (and other) outbreaks of disease, often as part of a mixed infection; in most cases such infections involve glucolytic strains of the A. calcoaceticus–A. baumannii complex– particularly A. baumannii
(also called group 2, or genospecies 2).
The most common manifestations of disease include septicaemia and infections of the urinary tract, lower respiratory tract and central nervous system. Transmission may occur by direct contact or may involve the airborne route.
Acinetobacters have been reported to survive on dry surfaces for at least as long as e.g. Staphylococcus aureus.
One problem associated with the pathogenic role of Acinetobacter is that these organisms appear easily to acquire resistance to antibiotics – so that they have the potential to develop as multiresistant pathogens.
Protocol ARPAC
PFGE method
Organism--------Acinetobacter baumannii
Recommended lysis enzyme:proteinase K
Restriction enzyme---------SmaI, ApaI
Approximate no. of---------20–40 , 20–30
restriction Fragments
Fragments size------------5–300,10–300
range (kb)
A.baumannii ACICU:
