[Durgical](https://durgical.com/en/) › [DurgiPedia](https://durgical.com/en/durgipedia/) › [Microbiology](https://durgical.com/en/microbiology/) › [Other Gram-negative rods](https://durgical.com/en/microbiology/groups/other-gram-negative-rods/) › Acinetobacter baumannii

[Microbiology](https://durgical.com/en/microbiology/) · [Other Gram-negative rods](https://durgical.com/en/microbiology/groups/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

## Key points

- Intensive care, ventilator and multidrug resistance: Acinetobacter.
- Oxidase-negative non-fermenting coccobacillus; survives on dry surfaces.
- WHO lists it as a critical priority pathogen for carbapenem resistance.
- Last-line options: sulbactam, polymyxins, tigecycline, cefiderocol.
- NCLEX: contact precautions and environmental cleaning.

## 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 →](https://durgical.com/en/conditions/sepsis-and-septic-shock/)
- Catheter-associated urinary infection [Urinary tract infection (acute cystitis) →](https://durgical.com/en/conditions/urinary-tract-infection/)
- 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:

- [Ampicillin + sulbactam](https://durgical.com/en/pharmacology/ampicillin-sulbactam/)
- [Colistin (colistimethate)](https://durgical.com/en/pharmacology/colistin/)
- [Polymyxin B](https://durgical.com/en/pharmacology/polymyxin-b/)
- [Tigecycline](https://durgical.com/en/pharmacology/tigecycline/)
- [Cefiderocol](https://durgical.com/en/pharmacology/cefiderocol/)
- [Meropenem](https://durgical.com/en/pharmacology/meropenem/)

## Prevention

- Hand hygiene and contact precautions
- Thorough cleaning and disinfection of the environment
- Early removal of invasive devices
- Antibiotic stewardship programs

## In Colombia

Carbapenem-resistant A. baumannii is a frequent cause of outbreaks in Colombian intensive care units; healthcare-associated infections are INS surveillance events.

## Memory aid

"Acinetobacter camps in the ICU": it settles, dry, on bed rails and ventilators and almost no antibiotic evicts it.

## 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.

[Add to my cards (4)](https://durgical.app/estudiar/?add=/en/microbiology/acinetobacter-baumannii/)

## Related

- [Pseudomonas aeruginosa](https://durgical.com/en/microbiology/pseudomonas-aeruginosa/)
- [Klebsiella pneumoniae](https://durgical.com/en/microbiology/klebsiella-pneumoniae/)

## Related conditions

- [Sepsis and septic shock](https://durgical.com/en/conditions/sepsis-and-septic-shock/)
- [Urinary tract infection (acute cystitis)](https://durgical.com/en/conditions/urinary-tract-infection/)

## What the colours mean

**Gram-positive**
Thick peptidoglycan wall: stains purple.

**Gram-negative**
Thin wall with an outer membrane: stains pink.

**Acid-fast**
Lipid-rich wall (mycobacteria): Ziehl–Neelsen stain.

**Contact**
Gown and gloves; dedicated equipment. For C. difficile, soap-and-water hand washing.

**Droplet**
Surgical mask within about a metre; single room.

**Airborne**
N95 respirator and a negative-pressure room.

[← Back to the group: Other Gram-negative rods](https://durgical.com/en/microbiology/groups/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](https://www.cdc.gov/acinetobacter/about/index.html) (CDC, 2025); [Antimicrobial resistance](https://www.who.int/news-room/fact-sheets/detail/antimicrobial-resistance) (WHO, 2026); [Fichas y Protocolos](https://www.ins.gov.co/buscador-eventos/Paginas/Fichas-y-Protocolos.aspx) (Instituto Nacional de Salud (INS), Colombia, 2026).

## **Spotted a mistake?** We are always improving for the community. Tell us what is wrong and our team will review it. Report a mistake

Representative model, for educational purposes only.

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License: CC BY 4.0 (https://creativecommons.org/licenses/by/4.0/). Cite as: DurgiPedia (durgical.com), https://durgical.com/en/microbiology/acinetobacter-baumannii/