Study demonstrates need for better identification, treatment of S. maltophilia BSI
Stenotrophomonas maltophilia was unexpectedly identified as the most common carbapenem-resistant, gram-negative pathogen to cause bloodstream infections between 2010 and 2015 in a retrospective cohort study of a large U.S. database.
“At Shionogi, we first became aware of the increasing importance of Stenotrophomonas maltophilia when large numbers of clinical isolates were randomly collected in our systematic surveillance studies,” Bin Cai, MD, PhD, senior director at Shionogi Inc., told Healio. “In addition, when speaking with clinical experts, we learned that some specific hospitals had longstanding experience with S. maltophilia, mainly bloodstream infections.”
Cai and colleagues examined patients with S. maltophilia bloodstream infection (BSI) in the United States using 2010-2015 data from the U.S. Premier Healthcare Database. According to the study, researchers assessed patient characteristics, infection characteristics, antibiotic treatment and discharge status.
According to Cai, the study demonstrated that S. maltophilia is the most common carbapenem-resistant, gram-negative pathogen causing BSI in the U.S. during the time period examined, a finding Cai says was unexpected but consistent across the U.S. over several years.
Study findings showed that, of 486 unique patients with S. maltophilia BSI, 44.6% were determined to be community onset, 95% of cultures were susceptible to trimethoprim-sulfamethoxazole (TMP-SMX) and 84% were susceptible to fluoroquinolones. Additionally, 39.1% of patients received a potentially effective antibiotic — including fluoroquinolone, doxycycline, ceftazidime, minocycline or TMP-SMX — during the empiric treatment period, whereas 85.8% did so during the definitive treatment period. The most common antibiotic used as definitive treatment was levofloxacin (48.9%). TMP-SMX was given to 38.3% of patients during the definitive period, but used infrequently empirically (10.5%).
Cai explained that these findings were unexpected because the CDC and other epidemiologic investigations of antimicrobial resistance do not consider S. maltophilia because the resistance to carbapenems and other antibiotics is intrinsic rather than acquired. There is no “clearly defined” standard of care for S. maltophilia BSI, according to the study results.
“Standard empirical treatment of BSI or sepsis does not include treatment for S. maltophilia. Consequently, there are delays in appropriate effective treatment of this pathogen. The treatment of choice, TMP/SMX, is often not used even after identification of S. maltophilia from the blood cultures,” Cai said. “Also, surprisingly, the presence of S. maltophilia BSI was most often community onset. In other words, the patients were admitted to the hospital with the infection, so consideration of this pathogen should not be restricted to patients who have been hospitalized for some time.”
Novel, more effective treatments are needed for the management of S. maltophilia BSI, Cai added.