Serratia endocarditis: antimicrobial management strategies and clinical outcomes

Objectives: The incidence of Serratia endocarditis is increasing, yet optimal treatment has not been defined. Our objective was to investigate the outcomes of patients with Serratia endocarditis by treatment strategy. Methods: We reviewed adult patients with definitive Serratia endocarditis at two independent health systems between July 2001 and April 2023. Combination therapy was defined as receipt of ≥2 in vitro active agents for ≥72 h. Results: Seventy-five patients were included; 64% (48/75) were male and 85% (64/75) were people who inject drugs. Compared with monotherapy, receipt of combination therapy was associated with lower rates of microbiological failure (0% versus 15%, P = 0.026) and 90 day all-cause mortality (11% versus 31%, P = 0.049). Antimicrobial discontinuation due to an adverse event was more common among patients receiving combination therapy compared with monotherapy (36% versus 8%, P = 0.058). Conclusions: In the largest series of Serratia endocarditis to date, combination antibiotic treatment was associated with improved outcomes. However, larger, prospective studies are warranted.