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.
Also called: Achromobacter xylosoxidans, Elizabethkingia meningoseptica, Chryseobacterium, Ochrobactrum, Chromobacterium violaceum
Quick facts
- Type
- Bacterium · 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
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 →
- Neonatal meningitis with high mortality (Elizabethkingia meningoseptica) Bacterial meningitis →
- Airway infection and exacerbations in cystic fibrosis (Achromobacter) Cystic fibrosis →
- Hospital pneumonia, catheter bacteraemia and device infections Healthcare-associated infections (CLABSI, CAUTI, VAP) →
- Sepsis with liver and lung abscesses after a skin wound (Chromobacterium violaceum) 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)
- Meropenem
- Piperacillin + tazobactam
- Ciprofloxacin
- 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
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.
Connections
← 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 Elizabethkingia | Elizabethkingia | CDC (CDC, 2024); Achromobacter Infections and Treatment Options (Antimicrobial Agents and Chemotherapy (ASM), 2020); Chromobacterium violaceum: A Review of an Unexpected Scourge (International Journal of General Medicine, 2021).
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Representative model, for educational purposes only.