Stenotrophomonas maltophilia

Today we saw a patient with S. maltophilia catheter related bacteremia.

Review of the microbiology of this organism here.

• Straight or slightly curved, motile gram negative rod
• Obligate aerobe, will grow best at 35 degrees
• Non-lactose fermenter, catalase positive, oxidase negative
• Will grow on blood agar and MacConkey -- and can be selected for using imipenem innoculated plates as they are carbepenem resistant organisms.

Can be found in the environment -- and in the hospital in multiple places, usually involving water. Patients who are infected are more likely to have:

• Prior antibiotic therapy
• Central venous catheters
• Neutropenia or cytotoxic chemotherapy
• ICU/Mechanical ventillation/Tracheostomy
• Malignancy or steroid use

The majority of cases are nosocomial; however, community acquired infections can occur.

Distinguishing between colonization and infection can be difficult, particularly for respiratory isolates. Bacteremia is a common presentation with an attributable mortality of up to 60%. ICU admission (APACHE more than 15), shock and thrombocytopenia are associated with mortality.

Endocarditis can occur, as can hospital acquired pneumonia, nosocomial meningitis, cellulitis and urinary tract infection.

TMP-SMX is the antimicrobial agent of choice (greater than 90% are sensitive). Combination with ticarcillin/clavulanate should be considered for serious infections. Quinolones may be a reasonable alternative in the TMP/SMX resistant or intolerant but consideration should also be given to combining them with ticarcillin/clavulinate.