Aerobic, nonfermentative, Gram-negative bacterium. Motile due to polar flagella. S. maltophilia are catalase-positive, oxidase-negative (which distinguishes them from most other members of the genus) and have a positive reaction for extracellular DNase.
It is an uncommon bacterium and human infection is difficult to treat.
Initially classified as Pseudomonas maltophilia, S. maltophilia was also grouped in the genus Xanthomonas before eventually becoming the type species of the genus Stenotrophomonas in 1993.
S. maltophilia frequently colonizes breathing tubes such as endotracheal or tracheostomy tubes, the respiratory tract and indwelling urinary catheters. Infection is usually facilitated by the presence of prosthetic material (plastic or metal), and the most effective treatment is removal of the prosthetic material (usually a central venous catheter or similar device).
In immunocompetent individuals, S. maltophilia is a relatively unusual cause of pneumonia, urinary tract infection, or blood stream infection; in immunocompromised patients, however, S. maltophilia is a growing source of and latent pulmonary infections.
S. maltophilia colonization rates in individuals with cystic fibrosis have been increasing.
Important considerations: The choice of an agent should be based on local antimicrobial sensitivities, site of infection, cost, and comorbid conditions. Generally, the most common agents/regimens are listed first. Listed dosages may need to be adjusted for renal dysfunction.
Bactrim 15 to 20 mg/kg/day (based on trimethoprim component) IV, given in equally divided doses every 6 to 8 hours.