Health protection – guidance

Stenotrophomonas maltophilia

The characteristics, diagnosis and epidemiology of Stenotrophomonas maltophilia.

Stenotrophomonas maltophilia is a Gram-negative bacterium found in a variety of environments including soil, water, and plants. It also occurs in the hospital environment and may cause bloodstream infections, respiratory infections, urinary infections and surgical-site infections.

Clinically-significant infections usually only occur in those with significantly impaired immune defences, such as severely immuno-compromised patients. Infections in previously healthy patients are unusual.

Risk factors pre-disposing a hospitalised patient towards infection include prior exposure to antimicrobials (especially broad-spectrum antibiotics), mechanical ventilation, and prolonged hospitalisation. It may also affect the lungs of patients with cystic fibrosis.


S. maltophilia does not readily spread between patients and is not a common cause of healthcare-associated infection. Hospital outbreaks for many pathogens, like Acinetobacter baumannii, are usually caused by a single strain. Apparent outbreaks attributed to S. maltophilia are frequently caused by multiple strains, implying acquisition from environmental sources as opposed to inter-patient spread.


S. maltophilia is resistant to many antibiotic classes such as cephalosporins, carbapenems, and aminoglycosides. This means that treatment options are relatively limited. However, most strains remain susceptible to co-trimoxazole which is regarded as the drug of choice for treating infections.


The Antimicrobial resistance and healthcare associated infections (AMRHAI) reference unit provides national reference facilities for many healthcare associated bacteria, including S. maltophilia.


See voluntary data reported to Public Health England for bacteraemias due to Pseudomonas species (spp.), Stenotrophomonas maltophilia in England, Wales, and Northern Ireland: