What is Stenotrophomonas maltophilia?

Stenotrophomonas maltophilia is a motile, gram-negative non-fermentative bacillus previously known as Pseudomonas maltophilia and Xanthomonas maltophilia. The bacterium is an obligate aerobe that is common throughout the environment, particularly in water.

Where is Stenotrophomonas maltophilia found?

  • Soil
  • Water
  • Contaminated medical solutions such as saline rinse solutions, or humidifier water
  • Contaminated medical devices such as catheters and breathing tubes

Who is at risk of Stenotrophomonas maltophilia infection?

Stenotrophomonas maltophilia is an opportunistic pathogen. Specifically, individuals with existing conditions such as cystic fibrosis, immunosuppression, organ transplantation, malignancies, chemotherapy, prior broad-spectrum antimicrobial therapy, or presence of an indwelling catheter and respiratory therapy equipment are at highest risk of infection. Stenotrophomonas maltophilia infection in intensive care unit (ICU) patients has been identified as an independent risk factor for mortality. Contaminated water or medical devices in hospital settings are the primary causes of infection.

Individuals with intact immune systems can also become infected if it enters the body via a contaminated wound or an infected catheter.

How is Stenotrophomonas maltophilia transmitted?

Contaminated water in a hospital setting can transmit Stenotrophomonas maltophilia to patients through:

  • Direct entry into the body, either through ingesting, bathing, or contaminated surgical instruments
  • Implantation of contaminated medical devices
  • Indirect contact from contaminated surfaces via health worker’s hands
  • Colonization of the oropharynx from tap water

What are the clinical manifestations of infection?

Some clinical presentations of Stenotrophomonas maltophilia infection include:

  • Bacteremia
  • Pneumonia
  • Urinary tract infection
  • Soft tissue infection
  • Ocular infection
  • Endocarditis
  • Meningitis

How is Stenotrophomonas maltophilia infection diagnosed?

As a common environmental bacterium, isolation of Stenotrophomonas maltophilia can represent colonization, but does not always indicate infection. Stenotrophomonas maltophilia isolation from normally sterile sites like blood, cerebrospinal fluid, or pleural fluid can confirm infection. Additionally, laboratory testing can biochemically identify the bacterium. Stenotrophomonas maltophilia can be cultured on a variety of laboratory media.

Is infection difficult to treat by antibiotics?

Yes; Stenotrophomonas maltophilia is inherently resistant to multiple antimicrobial agents that are used to treat gram-negative infections, such as cephalosporins, carbapenems, and aminoglycosides.

What is the treatment for infection by the bacterium?

For susceptible strains, trimethoprim-sulfamethoxazole is recommended as the primary antimicrobial therapy. Combination therapy can be given for life-threatening infections. The combination of trimethoprim/sulfamethoxazole and ticarcillin/clavulanate or trimethoprim/sulfamethoxazole and ceftazidime, if the isolate is susceptible to ceftazidime, can be administered.

If infection might have been acquired through a contaminated medical device, immediate removal of the device is strongly recommended. No vaccine is available for the prevention of infection.


  • Saad Nseir, et al. “Intensive care unit-acquired Stenotrophomonas maltophilia: incidence, risk factors, and outcome”. Critical Care 2006. Vol 10 No 5. 10:R143
  • C. Nicodemo and J. I. Garcia Paez. “Antimicrobial therapy for Stenotrophomonas maltophilia infections”. Eur J Clin Microbiol Infect Dis (2007) 26:229-237
  • Looney J., Muhlemann K., and Narita M. “Stenotrophomonas maltophilia: highly virulent pathogen or innocent bystander”. Lancet Infect Dis 2009.

Disclaimer: This information is provided for informational purposes only and not for the purpose of providing legal or medical advice. You should contact your physician or attorney to obtain advice with respect to any particular issue or problem.