Multidrug-resistant Acinetobacter baumannii (MDRAB)

Fact sheet
1 November 2010

MDRAB is an emerging pathogen in health care settings, especially in the intensive care setting.

Pathogen information

  • Acinetobacter is a gram-negative bacterium commonly found in soil and water. While there are many types or “species” of Acinetobacter that can cause human disease, Acinetobacter baumannii (A. baumannii) accounts for about 80% of reported infections.
  • Reservoir: A. baumannii live and multiply not only in soil and water, but also on the skin of healthy people, especially in health care settings. Acinetobacter can live on the skin and may survive in the environment for several days. Acinetobacter may also colonize or live in a patient without causing infection or symptoms, especially in tracheostomy sites or open wounds.
  • Acinetobacter appears to be particularly effective at acquiring genetic material from other organisms and thus rapidly developing drug resistance.

Clinical information

  • Manifestation: Ranges from pneumonia to serious blood or wound infections. Typical symptoms of pneumonia include fever, chills and cough. Infections can cause bacteremia, pneumonia/ventilator-associated pneumonia (VAP), meningitis, urinary tract infection, central venous catheter-related infection, and wound infection. Acinetobacter infection typically occurs in very ill patients and can either cause or contribute to death in these patients.
  • Treatment of infections caused by A. baumannii is guided by in vitro antimicrobial susceptibility assays, but an optimal treatment for A. baumannii infections has not been established, especially for MDRAB. Decisions on treatment should be made on a case-by-case basis by a health care provider. Clinicians should be guided in their choice of therapy by a knowledge of the susceptibility patterns of strains present in their own geographical area. Extensively resistant A. baumannii strains remain generally susceptible to polymyxins (colistin and polymyxin B). Combination therapy has also been used. Peptides and other novel antibacterial agents for A. baumannii infections are in the experimental phase.

Surveillance/survey information

  • Case definition: MDRAB is A. baumannii resistant to multiple antibiotics, often defined as three or more antimicrobials (e.g. aminoglycoside, ampicillin-sulbactam, antipseudomonal carbapenem, antipseudomonal cephalosporin, fluoroquinolone)
  • Many Member States have not yet established a comprehensive national antimicrobial resistance programme, although some estimates have been reported.a) Japan Nosocomial Infectious Surveillance, which includes 847 voluntary hospitals, reported that 35 (0.2%) of 14 755 Acinetobacter-positive samples were multidrug-resistant in 2008 and 32 (0.2%) of 16 929 Acinetobacter-positive samples were multidrug-resistant in 2009b) Although an active surveillance strategy has not been widely applied to MDRAB, A. baumannii is estimated to be responsible for 2%-10% of all gram-negative bacterial infections in intensive care units in Europe and the United States of America.

Source, route and risk factors of MDRAB infection


  • MDRAB infections occurs most often in Health care settings (hospital colonization and human reservoirs) housing very ill patients.
  • They rarely occur outside of health care settings; however, community-acquired A. baumannii has been reported in China and tropical Australia, and has been mostly identified in patients with co-morbidity.

Route of transmission

  • Acinetobacter can be spread by person-to-person contact, contact with contaminated surfaces, or exposure in the environment (by colonized medical equipment). Acinetobacter can enter through open wounds, catheters and breathing tubes. Careful attention to infection control procedures, such as, hand hygiene and environmental cleaning, can reduce the risk of transmission.

Risk factors

  • People who have weakened immune systems, chronic lung disease, or diabetes may be more susceptible to infections with Acinetobacter.
  • Hospitalized patients (particularly those in intensive care units), especially very ill patients on a ventilator, those with a prolonged hospital stay, or those who have open wounds (e.g. recent surgery or invasive procedure), are also at greater risk for Acinetobacter infection.


  • US Centers for Disease Control and Prevention (CDC):
  • Japan National Institute of Infectious Diseases (NIID), Infectious Disease Surveillance Centrer (IDSC):
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