ACINETOBACTER BAUMANNII: AN IMPORTANT OPPORTUNISTIC (RESISTANT) GRAM NEGATIVE BACTERIUM IN HUMAN POPULATION

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Acinetobacter baumannii is a Gram-negative, aerobic, oxidase-negative, and catalase-positive coccobacillus found in the genus Acinetobacter and family Moraxellaceae. Species of A. baumannii do not ferment sugars or carbohydrates and they are nitrate reduction negative. A. baumannii are mostly found in moist environments of hospital settings, and are responsible for causing a number of nosocomial infections such as respiratory illnesses. They also cause sepsis, pneumonia, wound infections and urinary tract infections in immunocompromised individuals. Generally, Acinetobacter species like Pseudomonas species are opportunistic pathogens in humans (especially the immunocompromised) even though they may exist as commensal organisms in the environment. A. baumannii also colonize hospital equipments and other invasive devices such as urine catheters and respirators. Strains of A. baumannii that are multidrug resistant are commonly found in the community and hospital environments where they cause several severities of morbidity in human population.      

A. baumannii are saprophytic organisms ubiquitously found in sewages, the soil and in water. A. baumannii are members of the normal microflora of the human skin and mucous membranes of the respiratory tract. Acinetobacter species are important food spoilage bacteria, and they mostly contaminate perishable food products such as poultry products, meat and seafood. Most importantly is the fact that Acinetobacter species easily acquire resistance to some commonly used antibiotics, and this makes antibiotic therapy difficult. A. baumannii can be cultivated in normal bacteriological culture media from clinical samples such as sputum and blood, and even from the moist areas of hospital environments. Other species of Acinetobacter that may be of less clinical importance include A. haemolyticus, A. johnsonii, A. calcoaceticus and A. lwoffii.

Further reading

Brooks G.F., Butel J.S and Morse S.A (2004). Medical Microbiology, 23rd edition. McGraw Hill Publishers. USA.

Gilligan P.H, Shapiro D.S and Miller M.B (2014). Cases in Medical Microbiology and Infectious Diseases. Third edition. American Society of Microbiology Press, USA.

Madigan M.T., Martinko J.M., Dunlap P.V and Clark D.P (2009). Brock Biology of Microorganisms, 12th edition. Pearson Benjamin Cummings Inc, USA.

Wilson B. A, Salyers A.A, Whitt D.D and Winkler M.E (2011). Bacterial Pathogenesis: A molecular Approach. Third edition. American Society of Microbiology Press, USA.

Woods GL and Washington JA (1995). The Clinician and the Microbiology Laboratory. Mandell GL, Bennett JE, Dolin R (eds): Principles and Practice of Infectious Diseases. 4th ed. Churchill Livingstone, New York.

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