“Intracellular lipid bodies of Acinetobacter baumannii”

Abstract

ABSTRACT: The World Health Organization lists Acinetobacter baumannii as one of the top three priority multidrug-resistant MDR pathogens. It was described as an opportunistic pathogen isolated from hospitalized patients. A. baumannii are Gram-negative, strictly aerobic, non-fermenting, non- fastidious, non-motile bacteria. It causes a wide range of nosocomial infections including ventilator-associated pneumonia (VAP), bacteraemia, skin and wound infections, infections of the urinary tract, and secondary meningitis associated with neurosurgical procedures. It is noted that Actinetobacter strains grow at different temperatures and pH levels and have the ability to use a variety of nutrition sources. This had lead to explains of how Acinetobacter species are capable of persisting in the hospital climate, either moist or dry conditions and survival, for maybe months, on surfaces and also in nature such as soil, water, food, and sewage. Several phenotypical similarities exist between this species and Acinetobacter calcoaceticus, leading them to be grouped as the A. baumannii calcoaceticus complex (ABC). According to Kalscheuer et al. (2003) A. calcoaceticus ADP1 accumulates the neutral lipids, wax esters and triacylglycerols (WS/TAGs) during the cultivation process in certain culture conditions. TAGs and wax esters are uncommon storage lipids in most bacteria apart from the Acinetobacter and many Actinomycetes such as Mycobacterium and Rhodococcus. A unique bifunctional enzyme wax ester synthase acyl CoA/diacylglycerol acyltransferase (WS/DGAT) catalysing the biosynthesis of both wax ester and TAG in A. calcoaceticus. However, the physiological functions of neutral lipid accumulation as lipid bodies (LB) have gained more attention in some species' biology than in A. calocaceticus. For example, LBes in bacilli during infection have been identified in Mycobacterium tuberculosis. There they are associated with phenotypic antibiotic resistance, and in Rhodococci LBs have been shown to be important in surviving various environmental habitat stresses, including desiccation. There is still a need to explore the role of neutral lipid (and LBs) in Acinetobacter species. It is hypothesised that Acinetobacter LBs can improve the survival of the environment and/or be essential for infection and specifically for A.baumannii.