Microbiology · Other Gram-negative rods
Acinetobacter baumannii !
- Bacterium
- Gram-negative
- Contact
- Exam priority: medium
An intensive care unit bacterium that survives on dry surfaces and resists nearly every antibiotic.
Updated 2026-11-01
At a glance
- Gram
- Gram-negative
- Shape
- Coccobacillus
- Oxygen
- Strict aerobe
- Family
- Moraxellaceae
- Stain
- Gram: red coccobacilli, sometimes hard to decolorize
Morphology
- Non-motile Gram-negative coccobacillus, often in pairs
- Non-fermenter, oxidase-negative (unlike Pseudomonas)
- Survives for weeks on dry surfaces and equipment
Transmission
- Contact with contaminated surfaces or equipment
- Hands of health workers
- Patients on ventilators, with catheters, surgical wounds or long stays
- Contact (on top of standard) for multidrug-resistant strains
Reservoir: Hospital environment (dry surfaces, equipment); Skin and airway of colonized patients
Isolation precautions
What the care team adds to standard precautions.
- Contact
- Gown and gloves; dedicated equipment. For C. difficile, soap-and-water hand washing.
Virulence factors
- Resistance to drying and biofilm formation
- OXA-type carbapenemases, efflux pumps and porin loss: multidrug resistance
- Picks up resistance genes very easily
- LPS and outer membrane proteins: inflammation and cell damage
Diseases it causes
- Ventilator-associated pneumonia
- Bacteremia and sepsis, mainly catheter-related Sepsis and septic shock →
- Catheter-associated urinary infection Urinary tract infection (acute cystitis) →
- Wound and burn infection (described in war wounds)
Diagnosis
- Culture of tracheal aspirate, blood, urine or wound
- Oxidase-negative, non-fermenting Gram-negative coccobacilli
- Extended susceptibility testing, including carbapenemase detection
- Separating colonization from true infection
Treatment
Guided by the antibiogram with infectious diseases input: for carbapenem-resistant strains, sulbactam (alone or combined), polymyxins (colistin, polymyxin B), tigecycline or cefiderocol, often in combination.
Drug class only; doses and regimens are set by the clinician from the current guideline.
In Pharmacology:
Prevention
- Hand hygiene and contact precautions
- Thorough cleaning and disinfection of the environment
- Early removal of invasive devices
- Antibiotic stewardship programs
Test yourself
Think of the answer, then tap the question to see it.
Which environmental trait explains Acinetobacter outbreaks in intensive care units?
It survives for a long time on dry surfaces and equipment and spreads by hands and contact.
Which biochemical test separates Acinetobacter from Pseudomonas?
Oxidase: Acinetobacter is oxidase-negative and Pseudomonas is oxidase-positive.
Which isolation precaution applies to a patient with multidrug-resistant Acinetobacter?
Contact precautions, on top of standard.
Which antibiotics are used for carbapenem-resistant strains?
Sulbactam, polymyxins (colistin or polymyxin B), tigecycline or cefiderocol, guided by the antibiogram.
Related
Related conditions
← Back to the group: Other Gram-negative rods
Educational content on microorganisms; not a treatment guide and no substitute for a health professional's advice. No doses are given.
Sources: About Acinetobacter (CDC, 2025); Antimicrobial resistance (WHO, 2026); Fichas y Protocolos (Instituto Nacional de Salud (INS), Colombia, 2026).
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Representative model, for educational purposes only.