P-1358. Efficacy of combination therapy with minocycline for the treatment of Stenotrophomonas maltophilia infections

Abstract Background Stenotrophomonas maltophilia is a multidrug-resistant bacterium that causes high in-hospital mortality worldwide. However, published data on the utility of combination therapy for S. maltophilia infections remain limited. Methods We enrolled adult patients with S. maltophilia infection in a randomized, double-blind, placebo-controlled, single-center clinical trial at Siriraj Hospital, Thailand. Patients were assigned 1:1 to receive minocycline capsules (100 mg twice daily) in combination with either levofloxacin or trimethoprim-sulfamethoxazole or monotherapy with either levofloxacin or trimethoprim-sulfamethoxazole. The study outcomes were 28-day mortality, clinical and microbiological responses, and adverse events. The favorable microbiological outcome was that the previously identified pathogen was not detected, and no new pathogen was detected. Results Between 2022 and 2024, 112 patients were randomly assigned to combination therapy (n = 55) or monotherapy (n = 57). Most patients were in the intensive care unit at the time of enrollment (71.4%). There was no difference in 28-day mortality between groups (43.6% combination therapy vs 38.6% monotherapy, p = 0.59). Patients on combination therapy had significantly more favorable microbiological outcomes than patients on monotherapy 72 hours after treatment (45.5% on combination therapy vs 14% on monotherapy, p < 0.001) and at the end of treatment (80% on combination therapy vs 56.1% on monotherapy, p = 0.023). However, we observed comparable favorable clinical response rates 72 hours after treatment and at the end of treatment (52.7% on combination therapy vs 42.1% on monotherapy, p = 0.30, and 54% on combination therapy vs 57% on monotherapy, p = 0.86, respectively). Acute kidney injury was independently associated with 28-day mortality per a multivariate analysis. Adverse events, including acute kidney injury (n = 65/112; 58%) and elevated liver enzymes (n = 8/112; 7%), occurred but were not related to the study drug. Conclusion Combination therapy with minocycline had better microbiological efficacy than monotherapy in patients with S. maltophilia infection and was safe. However, a beneficial effect of combination therapy with minocycline on the clinical outcomes of S. maltophilia infections was not noted. Disclosures All Authors: No reported disclosures