[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/) › Other non-fermenting Gram-negative rods

# Other non-fermenting Gram-negative rods

- Bacterium

## Gram-negative?

Thin wall with an outer membrane: stains pink.

## Contact?

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

- For completeness

Water and soil bacteria that cause hospital outbreaks or rare tropical infections and resist many common antibiotics.

Updated Nov 13, 2026

Also called: Achromobacter xylosoxidans, Elizabethkingia meningoseptica, Chryseobacterium, Ochrobactrum, Chromobacterium violaceum

## Quick facts

**Type**
Bacterium · [Other Gram-negative rods](https://durgical.com/en/microbiology/groups/other-gram-negative-rods/)

**Gram / shape**
Gram-negative · Rods

**Spread**
Contaminated hospital water · Outbreaks in neonatal

**Causes**
Bacteraemia in preterm newborns · Hospital pneumonia

**Treatment**
Treatment follows susceptibility testing

On this page

- The basics Key points
- At a glance
- Morphology
- Transmission
- In Colombia
- Memory aid
- What the colours mean

- Clinical Virulence factors
- Diseases it causes
- Clinical picture
- Diagnosis

- Treatment Treatment
- Prevention

- Study Test yourself

- Connections Connections

## Key points

- Neonatal meningitis in an outbreak linked to hospital water: Elizabethkingia meningoseptica.
- Elizabethkingia is a Gram-negative that resists carbapenems and colistin.
- Cystic fibrosis airway non-fermenters: Pseudomonas, Burkholderia, Stenotrophomonas and Achromobacter.
- Violet colonies, tropical wound and liver abscesses: Chromobacterium violaceum.

## At a glance

**Gram**
Gram-negative

**Shape**
Rods

**Oxygen**
Strict aerobes that do not ferment sugars; Chromobacterium is a facultative anaerobe grouped here by habit

**Family**
Several families (Alcaligenaceae, Weeksellaceae, Brucellaceae, Chromobacteriaceae)

## Morphology

- Achromobacter: motile Gram-negative rod, often mistaken for Pseudomonas
- Elizabethkingia and Chryseobacterium: non-motile, oxidase-positive rods with pale yellow colonies
- Chromobacterium violaceum: colonies with a striking violet pigment (violacein)

## Transmission

- Contaminated hospital water, sinks, solutions and medical devices (Achromobacter, Elizabethkingia, Ochrobactrum)
- Outbreaks in neonatal and intensive care units
- Chromobacterium: wounds exposed to soil or stagnant water in tropical regions

**Reservoir:** Soil, river water and plumbing; moist hospital environments

### 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

- Intrinsic resistance through efflux pumps and chromosomal beta-lactamases
- Elizabethkingia carries metallo-beta-lactamases that destroy carbapenems and resists colistin
- Biofilm on catheters and tubes
- Chromobacterium uses a type III secretion system and spreads fast to the liver and lungs

## Diseases it causes

- Bacteraemia in preterm newborns (Elizabethkingia) [Neonatal sepsis →](https://durgical.com/en/conditions/neonatal-sepsis/)
- Neonatal meningitis with high mortality (Elizabethkingia meningoseptica) [Bacterial meningitis →](https://durgical.com/en/conditions/bacterial-meningitis/)
- Airway infection and exacerbations in cystic fibrosis (Achromobacter) [Cystic fibrosis →](https://durgical.com/en/conditions/cystic-fibrosis/)
- Hospital pneumonia, catheter bacteraemia and device infections [Healthcare-associated infections (CLABSI, CAUTI, VAP) →](https://durgical.com/en/conditions/healthcare-associated-infections/)
- Sepsis with liver and lung abscesses after a skin wound (Chromobacterium violaceum) [Sepsis and septic shock →](https://durgical.com/en/conditions/sepsis-and-septic-shock/)

## Clinical picture

- Patients are usually premature babies, the critically ill or the immunocompromised
- Chromobacterium: a skin lesion after contact with water or mud, then rapid sepsis and abscesses; very high mortality
- Chronic granulomatous disease predisposes to Chromobacterium infection

## Diagnosis

- Culture on standard media; identification by MALDI-TOF mass spectrometry
- Violet colonies point to Chromobacterium
- Always request susceptibility testing: resistance patterns are unusual

## Treatment

Treatment follows susceptibility testing. Trimethoprim-sulfamethoxazole, piperacillin-tazobactam and carbapenems are often active against Achromobacter; Elizabethkingia resists carbapenems and colistin but may respond to fluoroquinolones, minocycline or trimethoprim-sulfamethoxazole; Chromobacterium resists penicillins and many beta-lactams and is treated with carbapenems, fluoroquinolones or aminoglycosides.

Drug class only; doses and regimens are set by the clinician from the current guideline.

In Pharmacology:

- [Sulfamethoxazole + trimethoprim (co-trimoxazole)](https://durgical.com/en/pharmacology/sulfamethoxazole-trimethoprim/)
- [Meropenem](https://durgical.com/en/pharmacology/meropenem/)
- [Piperacillin + tazobactam](https://durgical.com/en/pharmacology/piperacillin-tazobactam/)
- [Ciprofloxacin](https://durgical.com/en/pharmacology/ciprofloxacin/)
- [Minocycline](https://durgical.com/en/pharmacology/minocycline/)

## Prevention

- Water management and cleaning of sinks and drains in neonatal and intensive care units
- Sterile handling of solutions and devices
- Contact precautions and hand hygiene during outbreaks
- Clean wounds after contact with soil or fresh water in the tropics

## In Colombia

Chromobacterium violaceum lives in soil and water of tropical regions, and isolated cases have been reported in Colombia; it should be considered in sepsis after a wound exposed to water or mud.

## Memory aid

Picture a hospital sink with three tenants (Achromobacter, Elizabethkingia, Ochrobactrum) and a purple visitor from the tropical river (Chromobacterium).

## Test yourself

Think of the answer, then tap the question to see it.

## Which non-fermenter causes neonatal meningitis outbreaks linked to hospital water?

Elizabethkingia meningoseptica.

## Which colony feature identifies Chromobacterium violaceum?

A violet pigment called violacein.

## Which non-fermenter besides Pseudomonas and Burkholderia colonises the airways in cystic fibrosis?

Achromobacter xylosoxidans (and Stenotrophomonas maltophilia).

## Why is susceptibility testing essential for these organisms?

They have intrinsic resistance to many antibiotics, including carbapenems and colistin in Elizabethkingia.

[Add to my cards (4)](https://durgical.app/estudiar/?add=/en/microbiology/other-non-fermenting-gram-negative-rods/)

## 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.

## Connections

## Related 5

- [Pseudomonas aeruginosa](https://durgical.com/en/microbiology/pseudomonas-aeruginosa/)
- [Stenotrophomonas maltophilia](https://durgical.com/en/microbiology/stenotrophomonas-maltophilia/)
- [Acinetobacter baumannii](https://durgical.com/en/microbiology/acinetobacter-baumannii/)
- [Burkholderia cepacia complex and Burkholderia pseudomallei](https://durgical.com/en/microbiology/burkholderia-cepacia-complex-and-burkholderia-pseudomallei/)
- [Brucella](https://durgical.com/en/microbiology/brucella/)

## Related conditions 5

- [Neonatal sepsis](https://durgical.com/en/conditions/neonatal-sepsis/)
- [Bacterial meningitis](https://durgical.com/en/conditions/bacterial-meningitis/)
- [Cystic fibrosis](https://durgical.com/en/conditions/cystic-fibrosis/)
- [Healthcare-associated infections (CLABSI, CAUTI, VAP)](https://durgical.com/en/conditions/healthcare-associated-infections/)
- [Sepsis and septic shock](https://durgical.com/en/conditions/sepsis-and-septic-shock/)

[← 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 Elizabethkingia | Elizabethkingia | CDC](https://www.cdc.gov/elizabethkingia/about/index.html) (CDC, 2024); [Achromobacter Infections and Treatment Options](https://pmc.ncbi.nlm.nih.gov/articles/PMC7577122/) (Antimicrobial Agents and Chemotherapy (ASM), 2020); [Chromobacterium violaceum: A Review of an Unexpected Scourge](https://pmc.ncbi.nlm.nih.gov/articles/PMC8276824/) (International Journal of General Medicine, 2021).

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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/other-non-fermenting-gram-negative-rods/