Acinetobacter baumannii complex
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.