Clinical Characteristics of a Military Trauma Cohort with Stenotrophomonas maltophilia Infection

Background: Stenotrophomonas maltophilia is an emerging pathogen in critically ill trauma patients that has a unique resistance pattern often not covered by empiric antimicrobials. This study reveals the clinical epidemiology of patients with S. maltophilia isolates in a military trauma cohort.

Methods: Patients enrolled in the Trauma Infectious Disease Outcomes Study (TIDOS) from 9/09 to 2/14 with S. maltophilia isolation confirmed by BD Phoenix™ (NMIC/ID 304) panels were included. Patient demographics, injury, and infection data prospectively obtained from admission to Landstuhl Regional Medical Center (LRMC) through transfer and hospital stay at 3 continental US (CONUS) sites were reviewed. Isolates were deemed infecting if they met criteria defined previously within the TIDOS cohort.

Results: Of 2,699 patients, 65 patients with complete clinical data and S. maltophilia isolates were included. All injuries occurred in support of operations in Afghanistan. 63 (97%) had blast injuries of which 58 (92%) were from improvised explosive devices. Median age was 24 years (IQR 21,27) and 85% had an injury severity score >25. 32% had previously received broad-spectrum antimicrobials. Most isolates were from wounds (62%) or respiratory (26%), with the remaining from blood (8%), urine (2%), and other (2%). 60% of patients had associated infections of which 54% were skin and soft tissue infections, 10% osteomyelitis, 10% blood stream infections, 16% sepsis, and 10% pneumonia. Median time from injury to 1^st isolation was 8 days (IQR 4,16) with a longer time to 1^st isolation in patients with identified infection (p<0.01). 26 (40%) isolates were recovered at LRMC and 39 (60%) at CONUS sites. 40 patients with wound isolates had a median of 9 OR visits (IQR 4,14) after isolation and 85% had polymicrobial growth. Median duration of hospital stay was 73 days (IQR 37, 89). 6 patients died with median time from culture to death of 11 days (IQR 7,45).

Conclusion: Patients in this military cohort with S. maltophilia isolation were severely injured, had prolonged hospitalizations, and required multiple OR visits. In this population, wounds are the most common source of S. maltophilia isolates, often in association with polymicrobial infections.