483. Case–control Study Evaluating the Risk of Stenotrophomonas maltophilia Pneumonia in Patients with Previous Exposure to Meropenem

Background Stenotrophomonas maltophilia (SM) is a growing cause of opportunistic nosocomial infections with a mortality rate of 23–77%. Previous studies have identified the use of broad-spectrum antibiotics, specifically carbapenems, as a risk factor for SM infection, but these findings were limited to secondary endpoints. Meropenem’s overall broad-spectrum activity but limited SM activity may favor SM colonization and infection. Methods Adult patients admitted between January 2016 and July 2018 with available culture data were identified using data mining software. Cases were defined by a positive SM respiratory culture between days 2 and 60 of admission and receipt of antibiotic treatment. Controls were defined by a respiratory culture negative for SM during the same period. The primary endpoint was to evaluate the exposure to at least 48 hours of meropenem between cases and controls, with exposure defined as at least 48 hours of meropenem treatment with the last dose given within 15 days of respiratory culture. Secondary endpoints were to evaluate exposure to at least 7 days of meropenem or other antipseudomonal antibiotics. Results A total of 225 patients were included, 106 as cases and 119 as controls. Baseline demographics and age-adjusted Charlson comorbidity index score were similar between groups. Twenty-one cases (19.8%) and 5 controls (4.2%) were exposed to at least 48 hours of meropenem before developing SM pneumonia. The odds of meropenem exposure was 5 times greater in cases than controls (OR = 5.6, P < 0.001). After adjusting for a longer length of stay before culture collection as a potential confounding variable, meropenem use was still associated with SM pneumonia (adjusted OR = 4.6, 95% CI 1.7–14.7). Significant associations were also found with exposure to at least 7 days of meropenem (OR = 4.7, 95% CI 1.52–14.77, P = 0.004) or other antipseudomonal antibiotics (OR = 3.0, 95% CI 1.59–5.71, P < 0.001). Conclusion This is the first study to evaluate meropenem as a risk factor for developing SM pneumonia. Even as little as 48 hours of meropenem exposure increases the risk of developing SM pneumonia. As one of the few modifiable risk factors for SM infection, judicious use of meropenem may reduce the incidence of SM infection and associated mortality. Disclosures All authors: No reported disclosures.