Antimicrobial Susceptibility Profiles and Associated Clinical Risk Factors of Stenotrophomonas maltophilia Isolated from Blood Cultures: A Retrospective Study

Purpose Stenotrophomonas maltophilia is intrinsically resistant to multiple antimicrobial agents, resulting in limited therapeutic options when it is recovered from blood cultures. This study aimed to evaluate the antimicrobial susceptibility profiles of S. maltophilia bloodstream isolates, with particular attention to cefiderocol and aztreonam-avibactam, and to identify clinical factors associated with poor prognosis, ICU admission, and pulmonary infection among patients with S. maltophilia-positive blood cultures. Patients and Methods: This retrospective study included 90 S. maltophilia isolates recovered from blood cultures at Nanjing Drum Tower Hospital, China, between January 2012 and December 2025. Antimicrobial susceptibility testing of the 90 isolates was performed using the broth microdilution method. linical data were available for 86 corresponding patients and were collected from electronic medical records. Patients were stratified according to prognosis, ICU admission, and the presence of pulmonary infection. Univariate and multivariate logistic regression analyses were performed to identify independent associated factors. Results Among the 90 isolates, aztreonam-avibactam showed favorable in vitro activity, with MIC ₅₀ /MIC ₉₀ values of 8/8 µg/mL, and 94.4% of isolates were inhibited at concentrations of ≤ 8 µg/mL. Cefiderocol also demonstrated strong activity, with MIC ₅₀ /MIC ₉₀ values of 0.25/1 µg/mL, and 93.3% of isolates were inhibited at concentrations of ≤ 1 µg/mL. Among conventional agents, trimethoprim-sulfamethoxazole showed the highest susceptibility rate (98.9%), followed by levofloxacin (90.0%) and minocycline (45.6%). Complete baseline data were available for 86 patients, of whom 44 (51.2%) had a poor prognosis. Multivariate analysis showed that pulmonary infection was independently associated with poor prognosis (OR = 4.800; 95% CI: 1.645–14.002; P = 0.004) and ICU admission (OR = 4.004; 95% CI: 1.391–11.756; P = 0.010). Male sex (OR = 3.369; 95% CI: 1.038–10.935; P = 0.043) and antifungal agent use (OR = 3.043; 95% CI: 1.004–9.225; P = 0.049) were independently associated with pulmonary infection. Conclusion Cefiderocol and aztreonam-avibactam exhibited promising in vitro activity against S. maltophilia blood culture isolates, while trimethoprim-sulfamethoxazole remained the most active conventional agent. Pulmonary infection was strongly associated with poor prognosis and ICU admission, suggesting that respiratory involvement may represent an important clinical warning sign among patients with S. maltophilia-positive blood cultures.