Serratia marcescens endocarditis in a horse.

Serratia marcescens was the causative agent of bacterial endocarditis in a 2-year-old Arabian stallion. The horse was treated with broad-spectrum antibiotics for 1 month. The horse died several months after treatment was discontinued. To our knowledge, Serratia marcescens has not been reported as the cause of bacterial endocarditis in horses; however, multiple cases of bacterial endocarditis attributable to Serratia marcescens have been documented in human beings. The bacteria is most commonly isolated in immune-compromised patients.