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Acinetobacter baumanni

Also known as: A. baumannii, A. calcoaceticus–baumannii complex

Industry of interest: Healthcare

Classification: Bacterium

Microbiology: Acinetobacter is an oxidase-negative, non-fermentative, Gram-negative rod. The taxonomy of Acinetobacter is complex because considerable heterogeneity exists within the genus but the predominant species of medical importance are from the A. calcoaceticus–baumannii complex, including A. baumannii (Peleg et al. 2008),


Habitat and transmission: Acinetobacter commonly occurs in soil, is part of the natural skin flora of man and has been isolated from animals (Peleg et al. 2008). Colonization sites on the human body are not well described or understood.

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Disease and symptoms: Acinetobacter are rarely implicated as a cause of disease in healthy individuals. For this reason, Acinetobacter isolated from clinical specimens was largely ignored until the 1970s when diseases caused by Acinetobacter became increasing recognised (Joly-Guillou 2005). A. baumannii has relatively low virulence compared with other nosocomial pathogens, such as MRSA, and are largely restricted to severely ill patients in critical care environments. In these environments, A. baumannii can cause pneumonia, tracheobronchitis, bloodstream infections, urinary tract infections, cathether-related infections and rarely wound infections (Joly-Guillou 2005). Although the infections caused by A. baumannii are typically “low-grade”, due to the severely ill nature of the patient affected, crude mortality is high typically ranging from 20-60% and attributable mortality is approximately 10-20% (Joly-Guillou 2005; Falagas and Rafailidis 2007).

Treatment and antibiotic resistance: A. baumannii has progressively acquired resistance to many antibiotics. Consequently the carbapenems have become the therapy of choice for serious A. baumannii infection (Joly-Guillou 2005). However, carbapenem-resistance has emerged (conferred by transferable resistance genes such as OXA-23 and -23, VIM, IMP and NDM-1), meaning that old antibiotics with reduced efficacy and increased side effects, such as colistin, have to be used to treat serious A. baumannii. infection (Coelho et al. 2004).

Prevention and control: Screening for colonization with A. baumannii is rarely performed so identification relies on clinically-indicated cultures. Therefore, hand-hygiene, isolation of infected or colonized patients and stringent environmental hygiene are necessary for the effective control of A. baumannii (Karageorgopoulos and Falagas 2008).

A. baumannii is shed into the environment by infected patients and can survive for extend periods on environmental surfaces (Kramer et al. 2006; Thom et al. 2011). Outbreak reports highlight the importance of environmental decontamination in the control of A. baumannii (Catalano et al. 1999; Denton et al. 2004). Admission to a room previously occupied by a patient with A. baumannii increased the chances of A. baumannii acquisition (Nseir et al. 2011). Bioquell hydrogen peroxide vapour (HPV) is effective against A. baumannii in vitro (Otter and French 2009)and is more effective than bleach disinfection for the decontamination of A. baumannii on hospital surfaces (Manian et al. 2011). There is evidence that HPV can be useful for controlling the spread of A. baumannii and other Gram-negative bacteria during outbreaks and in endemic settings (Donegan et al. 2010; Manian et al. 2010; Otter et al. 2010; Gopinath et al. 2011; Kaiser et al. 2011).



Catalano, M., Quelle, L.S., Jeric, P.E., Di, M.A. and Maimone, S.M. (1999) Survival of Acinetobacter baumannii on bed rails during an outbreak and during sporadic cases. J Hosp Infect 42, 27-35.

Coelho, J., Woodford, N., Turton, J. and Livermore, D.M. (2004) Multiresistant acinetobacter in the UK: how big a threat? J Hosp Infect 58, 167-169.

Denton, M., Wilcox, M.H., Parnell, P., Green, D., Keer, V., Hawkey, P.M., Evans, I. and Murphy, P. (2004) Role of environmental cleaning in controlling an outbreak of Acinetobacter baumannii on a neurosurgical intensive care unit. J Hosp Infect 56, 106-110.

Donegan, N., Cruxton, M., Jones, M., Farrare-Wilmore, P., Geiser, K. and Pic-Aluas, L. (2010) Vaporized hydrogen peroxide as part of a control intervention during an outbreak of Acinetobacter in an ICU. SHEA 2010.

Falagas, M.E. and Rafailidis, P.I. (2007) Attributable mortality of Acinetobacter baumannii: no longer a controversial issue. Crit Care 11, 134.

Gopinath, R., Savard, P., Landrum, M., O'Connor, B., Wilson, L., Carroll, K. and Perl, T.M. (2011) Management of a NDM-1-producing Klebsiella pneumoniae: infection control and medical implications. IDSA 2011.

Joly-Guillou, M.L. (2005) Clinical impact and pathogenicity of Acinetobacter. Clin Microbiol Infect 11, 868-873.

Kaiser, M., Elemendorf, S., Kent, D., Evans, A., Harrington, S.M. and McKenna, D. (2011) Management of a multi-year MDR Acinetobacter baumannii outbreak in the ICU setting. IDSA 2011.

Karageorgopoulos, D.E. and Falagas, M.E. (2008) Current control and treatment of multidrug-resistant Acinetobacter baumannii infections. Lancet Infect Dis 8, 751-762.

Kramer, A., Schwebke, I. and Kampf, G. (2006) How long do nosocomial pathogens persist on inanimate surfaces? A systematic review. BMC Infect Dis 6, 130.

Manian, F.A., Griesenauer, S. and Senkel, D. (2010) Impact of an intensive terminal cleaning and disinfection (C/D) protocol involving selected hospital rooms on endemic nosocomial infection (NI) rates of common pathogens at a tertiary care medical center. SHEA 2010.

Manian, F.A., Griesenauer, S., Senkel, D., Setzer, J.M., Doll, S.A., Perry, A.M. and Wiechens, M. (2011) Isolation of Acinetobacter baumannii complex and methicillin-resistant Staphylococcus aureus from hospital rooms following terminal cleaning and disinfection: can we do better? Infect Control Hosp Epidemiol 32, 667-672.

Nseir, S., Blazejewski, C., Lubret, R., Wallet, F., Courcol, R. and Durocher, A. (2011) Risk of acquiring multidrug-resistant Gram-negative bacilli from prior room occupants in the ICU. Clin Microbiol Infect 17, 1201-1208.

Otter, J.A. and French, G.L. (2009) Survival of nosocomial bacteria and spores on surfaces and inactivation by hydrogen peroxide vapor. J Clin Microbiol 47, 205-207.

Otter, J.A., Yezli, S., Schouten, M.A., van Zanten, A.R., Houmes-Zielman, G. and Nohlmans-Paulssen, M.K. (2010) Hydrogen peroxide vapor decontamination of an intensive care unit to remove environmental reservoirs of multidrug-resistant gram-negative rods during an outbreak. Am J Infect Control 38, 754-756.

Peleg, A.Y., Seifert, H. and Paterson, D.L. (2008) Acinetobacter baumannii: emergence of a successful pathogen. Clin Microbiol Rev 21, 538-582.

Thom, K.A., Johnson, J.K., Lee, M.S. and Harris, A.D. (2011) Environmental contamination because of multidrug-resistant Acinetobacter baumannii surrounding colonized or infected patients. Am J Infect Control 39, 711-715.


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