Stenotrophomonas maltophilia
- 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.- Exam priority: medium
A water bacterium that infects very sick hospital patients and resists most antibiotics, including carbapenems.
Also called: Steno
Quick facts
- Type
- Bacterium · Other Gram-negative rods
- Gram / shape
- Gram-negative · Straight rod
- Spread
- Hospital water
- Causes
- Hospital-acquired · Chronic airway colonisation
- Treatment
- Trimethoprim-sulfamethoxazole is the first-line drug
At a glance
- Gram
- Gram-negative
- Shape
- Straight rod
- Oxygen
- Obligate aerobe; does not ferment glucose
- Family
- Lysobacteraceae (formerly Xanthomonadaceae)
Morphology
- Motile Gram-negative rod with polar flagella
- Usually oxidase-negative, unlike Pseudomonas aeruginosa
- Forms biofilm on plastic, glass and catheters
Transmission
- Hospital water: taps, sink drains, ice machines, nebulisers and respiratory equipment
- Colonised devices such as central lines and endotracheal tubes
- Hands of health workers can carry it between patients
Reservoir: Water, soil and plant roots; moist hospital surfaces
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
- Biofilm on catheters and airway tissue protects it from drugs and immune cells
- L1 metallo-beta-lactamase destroys carbapenems; L2 cephalosporinase adds resistance to cephalosporins
- Efflux pumps and low membrane permeability give intrinsic multidrug resistance, including to aminoglycosides
Diseases it causes
- Hospital-acquired and ventilator-associated pneumonia Hospital-acquired and ventilator-associated pneumonia →
- Catheter-related bloodstream infection and other device infections Healthcare-associated infections (CLABSI, CAUTI, VAP) →
- Chronic airway colonisation in cystic fibrosis Cystic fibrosis →
- Severe, sometimes haemorrhagic pneumonia in patients with neutropenia or blood cancers Febrile neutropenia →
- A typical multidrug-resistant hospital pathogen MRSA and other multidrug-resistant organism infections →
Clinical picture
- Typical patient: ICU stay, mechanical ventilation, central line, cancer and prior broad-spectrum antibiotics
- Often appears as a breakthrough infection during carbapenem therapy
- Sputum isolates often reflect colonisation; judge by the clinical picture
Diagnosis
- Grows on standard media; non-fermenting, usually oxidase-negative Gram-negative rod
- Identification by MALDI-TOF mass spectrometry
- Susceptibility testing is essential; separate infection from colonisation
Treatment
Trimethoprim-sulfamethoxazole is the first-line drug; levofloxacin and minocycline are alternatives, and cefiderocol or ceftazidime-avibactam combined with aztreonam are reserved for highly resistant isolates. It is intrinsically resistant to carbapenems and aminoglycosides; remove infected catheters.
Drug class only; doses and regimens are set by the clinician from the current guideline.
In Pharmacology:
- Sulfamethoxazole + trimethoprim (co-trimoxazole)
- Levofloxacin
- Minocycline
- Cefiderocol
- Ceftazidime + avibactam
- Aztreonam
Prevention
- Hand hygiene and contact precautions when the isolate is multidrug-resistant
- Water-safety plans for taps, sinks and respiratory equipment
- Careful central-line care and early removal
- Antimicrobial stewardship: carbapenem use selects for it
Test yourself
Think of the answer, then tap the question to see it.
Which first-line drug is used for Stenotrophomonas maltophilia infection?
Trimethoprim-sulfamethoxazole.
Why does Stenotrophomonas often appear in patients already receiving carbapenems?
Its chromosomal L1 metallo-beta-lactamase destroys carbapenems, so carbapenem use selects for it.
Which hospital reservoirs are linked to Stenotrophomonas?
Water sources such as taps, sink drains and ice machines, and respiratory or intravascular devices.
Which simple test helps separate Stenotrophomonas from Pseudomonas aeruginosa?
The oxidase test: Stenotrophomonas is usually oxidase-negative, Pseudomonas oxidase-positive.
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: Stenotrophomonas maltophilia: an Emerging Global Opportunistic Pathogen (Clinical Microbiology Reviews (ASM), 2012); Antimicrobial Treatment Strategies for Stenotrophomonas maltophilia: A Focus on Novel Therapies (Antibiotics (MDPI), 2021).
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Representative model, for educational purposes only.