Acinetobacter baumani - MegaMicro

Structure:  Strictly aerobic, non-lactose fermenting, oxidase negative, Gram negative coccobacillus.  Over 30 species have been identified; however, only 5 are associated with human disease, the majority by Acinetobacter baumannii.

Epidemiology:

• Reservoir: naturally inhabits soil and water; colonizes skin, wounds, respiratory and GI tracts.  

• Most particularly involved in hospital-associated (HA) infections in debilitated patients in ICU as well as infections associated with natural disasters and wars.

• Some strains can survive environmental desiccation for weeks, contributing to their ability to create outbreaks via contaminated fomites.

Pathobiology:

• Virulence factors: biofilm formation enhanced by the presence of pili, biofilm-associated protein (Bap) and outer membrane protein A (OmpA).

• K1 capsule present in approximately one-third of the strains; delays complement activation and phagocytosis.

Disease Manifestations:

• Particularly noted for Hospital-aquired, ventilator-associated pneumonia and central-line associated bacteremia.  

• Also involved in indwelling-catheter urinary tract infections, burn, surgical and traumatic wound infections.

Laboratory diagnosis:

• Bacterial culture: readily grows on routine culture media.

• Send sputum, blood, body fluid, wound and tissue samples as appropriate.

Differential diagnosis: Other bacterial Hosptital aquired infections

Treatment:

• Increasingly difficult to treat with the emergence of multi-drug resistant (MDR) strains.  Specific therapy should be guided by the in vitro susceptibility test results.

• Antibiotic susceptible strains:  ceftazidime or cefepime, a carbapenem or ampicillin-sulbactam.

• Antibiotic resistant strains:  polymyxins (polymyxin B or colistin), minocycline or tigecycline.

Prevention and control:

• Strict adherence to infection control protocols, hand hygiene and disinfection practices to prevent environmental contamination and patient to patient transmission.

• Limit use of broad-spectrum antibiotics.