38. Predicting stenotrophomonas Maltophilia bloodstream Infections (BSI) in the Hematologic Malignancy Population

Background Trimethoprim-sulfamethoxazole (TMP-SMX) is the preferred treatment for S. maltophilia BSI. Hematologic malignancy patients are at increased risk of S. maltophilia BSI but because of the TMP-SMX adverse event profile, this agent is not routinely included in empiric treatment regimens. We sought to identify risk factors for S. maltophilia BSI in hematologic malignancy patients to guide empiric treatment decisions in this population. Methods Inpatients ≥ 12 years at Johns Hopkins Health System hospitals between 7/1/16-12/1/19 with a hematologic malignancy and/or stem cell transplant (SCT) within 12 months were included. Cases were patients with S. maltophilia BSI and controls were patients with BSI from Gram-negative organisms other than S. maltophilia. Demographics, pre-existing medical conditions, antibiotic use (including prophylaxis) in the previous 3 months, and hospitalization in the previous 3 months were compared between cases and controls using non-parametric methods and multivariable logistic regression. Results There were 20 cases and 105 controls. Cases and controls were similar in terms of age, sex, type of underlying malignancy, proportion with recent SCT, absolute neutrophil count, (ANC), central venous catheter, and severity of illness. Cases were more likely to have received ≥ 72 hours of a carbapenem within the preceding 3 months, controlling for age, recent SCT, ANC, and central venous catheter (OR=3.11, 95% 1.05–9.16, p=0.04). There were no significant differences in prior cefepime or piperacillin/tazobactam use in the preceding 3 months between cases and controls. Conclusion Hematologic malignancy patients who received ≥ 72 hours of carbapenem therapy, but not other broad spectrum antibiotic use within the previous 3 months were more likely to be infected with S. maltophilia BSI. Identifying patients at high risk for S. maltophilia BSI can ensure early, appropriate empiric therapy – ultimately improving clinical outcomes. Disclosures All Authors: No reported disclosures