baumannii

Acinetobacter baumannii is a Gram‑negative, non‑motile, aerobic coccobacillus belonging to the family Moraxellaceae. It is oxidase‑negative, catalase‑positive, and typically forms smooth, circular colonies on routine laboratory media. The organism is widely distributed in the environment, inhabiting soil, water, and hospital surfaces, and can survive desiccation for prolonged periods.

Clinically, A. baumannii is an important opportunistic pathogen, especially in intensive‑care units. It is associated with a range of infections, including ventilator‑associated pneumonia, bloodstream infections, wound and burn infections, and urinary tract infections. The bacterium disproportionately affects patients with prolonged hospital stays, invasive devices, or compromised immunity.

A hallmark of A. baumannii is its capacity for extensive antimicrobial resistance. Multidrug‑resistant (MDR) and extensively drug‑resistant (XDR) strains produce β‑lactamases (including carbapenemases such as OXA‑23, OXA‑24/40, and OXA‑58), modify target sites, and employ efflux pumps. These mechanisms have rendered many isolates resistant to carbapenems, aminoglycosides, fluoroquinolones, and often colistin, complicating therapeutic options. Combination therapy, high‑dose sulbactam, tigecycline, and newer agents such as cefiderocol are used under susceptibility guidance.

Epidemiologically, A. baumannii outbreaks are frequently linked to contaminated equipment, respiratory therapy devices, and healthcare worker hands. Infection control measures—strict hand hygiene, environmental cleaning, patient isolation, and antimicrobial stewardship—are critical to limiting spread.

Research continues into novel anti‑A. baumannii agents, phage therapy, and vaccines, as well as rapid diagnostic methods to identify resistance determinants. Understanding the organism’s genetics, biofilm formation, and survival strategies remains essential for developing effective interventions against this increasingly formidable nosocomial pathogen.