S. maltophilia is an environmental multi-drug resistant Gram-negative bacteria that is mostly found as a respiratory tract colonizer in patients with cystic fibrosis (CF) and as an opportunist in immunocompromised hosts. To understand the role of this pathogen in non-CF patients, we performed a retrospective analysis of hospitalized patients with S. maltophilia empyema in the Veterans Health Administration (VHA).
Using microbiology results within the VHA Corporate Data Warehouse, we identified pleural fluid cultures that tested positive for S. maltophilia among 1.9 million hospitalized patients between January 1, 2010 and December 31, 2017. We then reviewed the electronic health records for these patients and collected demographics, clinical characteristics, microbiology, antibiotic treatment, and outcome (30-day mortality).
We identified 45 unique patients with S. maltophilia in pleural fluid cultures from 21 VHA facilities. Associated conditions included prolonged chest tube presence (n=35), recent hospital admission (n=34), recent antibiotic exposure (n=30), cancer (n=25), recent ICU stay (n=23), and cardiothoracic surgery (n=21). Most cultures were polymicrobial (n=36), with the most commonly isolated organisms being Enterobacteriaceae (n=12), Staphylococcus spp. (n=11), and Pseudomonas aeruginosa (n=9). According to susceptibility testing, trimethoprim-sulfamethoxazole (TMP-SMX) was the most active agent (93% susceptible), followed by levofloxacin (85%). Only 49% of tested isolates were susceptible to ceftazidime. In 27 (60%) of the cases, treatment directed against S. maltophilia was administered with TMP-SMX (n=16), levofloxacin (n=7) and minocycline (n=4). In 2 cases S. maltophilia was considered a contaminant since there was no evidence of pleural infection. In both groups, 30-day mortality was 22% (6/27 treated vs. 4/18 untreated).
S. maltophilia is infrequently isolated from pleural fluid among patients in the VHA system and is commonly a polymicrobial infection following instrumentation or surgery. In this cohort, we observed a high mortality independent of treatment, likely reflecting host co-morbidities or ineffective treatments.
B. Wilson, None
F. Perez, None
R. A. Bonomo, None