Serratia endocarditis. A follow-up report.

Seventeen new cases of Serratia marcescens endocarditis observed in the San Francisco Bay Area since June 1974 are presented. Fifteen patients had a history of illicit intravenous drug use and four patients had prosthetic heart valves. Seven patients with infection of right-sided heart valves did well, although surgery was required in two for persistent fever or recurrent pulmonary emboli. Only three of ten patients with left-sided infection survived despite synergistic antibiotic combinations and high serum bactericidal titers. Fifteen isolates of Serratia from patients with endocarditis were serotyped, and none of these serotypes corresponded to the pigmented strain aerosolized by the US Army in the Bay Area in 1951. The isolation of the same Serratia strain from two patients and their shared injection paraphernalia provided insight into the pathogenesis of endocarditis in the intravenous drug user. A revised therapeutic approach to this difficult infection is presented.