Stenotrophomonas maltophilia is an opportunistic bacterial pathogen previously known as Pseudomonas maltophilia and Xanthomonas maltophilia. Stenotrophomonas is of most concern in the hospital setting. This organism is inherently resistant to multiple antimicrobial agents that are used to treat gram-negative infections. Contaminated water can transmit the organism through indwelling catheters and respiratory therapy equipment to susceptible patients causing infection. Stenotrophomonas infection in intensive care unit (ICU) patients has been identified as an independent risk factor for mortality.

Test Method 

Filter concentration method using Trypticase Soy Agar with imipenem selective media, incubation 36.5°C + 0.5°C for 48hr–72hr.  Direct plating is also included in the event of high concentrations of the organism.  Modification of the ASTM International Standard Test Method for the Isolation and Enumeration of Pseudomonas aeruginosa from water [D 5246-92 (Reapproved 2004)]

Turn Around Time 

2–10 days

Test Code



The sample volume is ≥120 mL and should be collected as follows:

  1. Complete the Chain of Custody Test Request form.
  2. Use waterproof pen to label bottle with sample location, description, and date.
  3. Turn on hot water and immediately fill the bottle. Close bottle and invert to mix neutralizer.

Sample Transport 

  1. Ship the same day samples are collected for receipt in laboratory. The time from sample collection to analysis should not exceed 30 hours.
  2. Place bottles in box with insulated liner.
  3. Place completed Chain of Custody Test Request form in plastic document holder and pack in box.
  4. Ship overnight Monday–Thursdayonly to: Special Pathogens Laboratory, 1401 Forbes Avenue, Suite 401, Pittsburgh, PA 15219

Samples received on Saturday will not be processed.

Questions? Call 412-281-5335