Acinetobacter ursingii is a Gram-negative, non-fermentative, opportunistic bacterium belonging to the genus Acinetobacter. It is an uncommon species compared to Acinetobacter baumannii, but it has been increasingly recognized in healthcare-associated infections (HAIs). Reported cases include bacteremia, septicemia, pneumonia, urinary tract infections, and bloodstream infections, particularly in immunocompromised or hospitalized patients.
Morphology
Fig. Acinetobacter ursingii growth on blood agar
Gram Stain: Gram-negative coccobacilli, often appearing as short rods.
Produces biofilms, enhancing persistence in hospital environments and on medical devices.
Emerging reports of multidrug resistance complicate management.
Laboratory Diagnosis
Fig. Numerous pink to red-stained bacilli, arranged in short rods and elongated chains of Acinetobacter ursingii, while some appear slightly curved, while others are in clusters or dispersed individually
Culture: Growth on blood agar, MacConkey agar. Colonies may resemble other Acinetobacter spp.
Identification:
Conventional biochemical testing may misidentify the species.
Accurate identification requires MALDI-TOF MS or molecular sequencing (16S rRNA, rpoB gene).
Antimicrobial Susceptibility Testing (AST): Performed by CLSI/EUCAST broth microdilution or automated systems.
Fig. Acinetobacter ursingii in Gram stain
Treatment
Most strains are susceptible to a wider range of antibiotics than A. baumannii, but resistance is increasing.
Therapeutic options:
Beta-lactams (piperacillin-tazobactam, cephalosporins, carbapenems in some cases).
Fluoroquinolones, aminoglycosides, tetracyclines.
Multidrug-resistant isolates: May require colistin or combination therapy.
Therapy should always be guided by susceptibility testing.
Fig. Acinetobacter ursingii in Gram staining at a magnification of 4000XFig. Gram-negative cocobacilli to Gram-negative rods of Acinetobacter ursingii in Gram staining of culture microscopy at a magnification of 4000XFig. Acinetobacter ursingii in a Gram stain of culture
Prevention
Fig. Acinetobacter ursingii in Gram staining of culture microscopy at a magnification of 4000X
Infection control measures in hospitals (hand hygiene, device care, surface disinfection).
Judicious antibiotic use to prevent resistance selection.
Active surveillance in ICUs and oncology wards.
Strict sterilization of indwelling medical devices.
Keynotes
Fig. Gram negative coccobacilli to large Gram-negative rods of Acinetobacter ursingii in Gram staining of culture
Acinetobacter ursingii is a rare but emerging opportunistic pathogen in hospital settings.
Causes primarily bloodstream and device-associated infections in immunocompromised patients.
Often misidentified without molecular or MALDI-TOF confirmation.
Treatment outcomes are generally better than for A. baumannii, but resistance is rising.
Strong infection prevention practices are essential to reduce transmission.
