Question
Acinetobacter
Answer
Acinetobacter (notably A. baumannii) is a Gram-negative, strictly aerobic, non-motile coccobacillus, increasingly important as a multidrug-resistant nosocomial (hospital-acquired) pathogen, particularly in intensive care unit settings.
Key features: catalase-positive, oxidase-negative (distinguishing it from Pseudomonas species, which are oxidase-positive); grows readily on ordinary laboratory media (MacConkey agar — non-lactose fermenting colonies); notable for its ability to survive for prolonged periods on dry inanimate hospital surfaces (ventilators, bed rails, medical equipment), making it a persistent source of nosocomial outbreaks.
Clinical significance: causes ventilator-associated pneumonia, bloodstream infections/catheter-related bacteraemia, wound and burn infections (notably associated with combat/trauma wound infections), urinary tract infections, and post-neurosurgical meningitis — almost exclusively in hospitalized, critically ill, or immunocompromised patients.
Antimicrobial resistance: notorious for multidrug resistance (MDR) and even extensively/pan-drug resistance (XDR/PDR), mediated by multiple mechanisms — beta-lactamases (including carbapenemases, e.g., OXA-type enzymes), efflux pumps, porin loss, and aminoglycoside-modifying enzymes — often leaving only colistin, tigecycline, or carbapenem-sparing combination regimens effective, making it one of the WHO’s priority pathogens for new antibiotic development.
Infection control: strict contact precautions, environmental disinfection (given its surface-survival capacity), hand hygiene, and antibiotic stewardship are essential to prevent hospital outbreaks.