Stenotrophomonas maltophilia is an aerobic, nonfermentative, Gram-negative bacterium. 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 are slightly smaller (0.7–1.8 × 0.4–0.7 micrometers) than other members of the genus. They are motile due to polar flagella and grow well on MacConkey agar producing pigmented colonies. 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.
S. maltophilia is ubiquitous in aqueous environments, soil and plants, including water, urine, or respiratory secretions; it has also been used in biotechnology applications. In immunocompromised patients, S. maltophilia can lead to nosocomial infections.
S. maltophilia is naturally resistant to many broad-spectrum antibiotics (including all carbapenems) and is thus often difficult to eradicate. Many strains of S. maltophilia are sensitive to co-trimoxazole and ticarcillin, though resistance has been increasing. It is not usually sensitive to piperacillin, and sensitivity to ceftazidime is variable.
Stenotrophomonas maltophilia is a Gram negative bacterium that is commonly found in the environment. It is intrinsically multi-drug resistant and occasionally causes bacteraemic and organ-specific infections in humans.