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A Case of Mixed Serratia marcescens and Streptococcus mitis Endocarditis and Review of the Literature

Sanchez, Kathryn T. MD; Johnson, Leonard B. MD; Szpunar, Susan PhD; Saravolatz, Louis D. MD

Infectious Diseases in Clinical Practice: July 2012 - Volume 20 - Issue 4 - p 245–247
doi: 10.1097/IPC.0b013e318242430c
Review Articles

Bacterial endocarditis due to Serratia species typically involves left-sided heart valves and is associated with a high mortality rate. We describe a case of polymicrobial Serratia marcescens and Streptococcus mitis tricuspid valve infection successfully treated with medical therapy. A review of the literature revealed 73 cases of endocarditis due to Serratia species, including 16 cases (21.9%) with mixed infection. Endocarditis due to Serratia is most frequently seen among injection drug users, and most cases (73.2%) involve left-sided valves. There is a high mortality rate (58.3%) overall, and risk factors for death included involvement of left-sided valves (odds ratio, 19.5; 95% CI, 3.0–126.4; P = 0.002) and evidence of metastatic infection (odds ratio, 8.5; 95% CI, 1.1–64.4; P = 0.039). Polymicrobial endocarditis involving Serratia species also has a high mortality rate (60%) and a predilection for left-sided valves (75%). Whereas our case recovered with a 6-week combination antibiotic regimen, the optimal treatment strategy is unknown.

Sanchez et al. present a case of tricuspid valve endocarditis due to mixed Serratia marescens and Streptococcus mitis treated successfully with antibiotics alone. They reviewed the literature for cases of Serratia endocarditis and demonstrated a high mortality rate. In addition, left-sided endocarditis and evidence of metatstatic infections were associated with increased mortality

From the Department of Internal Medicine, St. John Hospital and Medical Center, Detroit, MI.

Correspondence to: Leonard B. Johnson, MD, 19251 Mack Ave, Suite 340, Grosse Pointe Woods, Michigan 48236. E-mail:

The authors have no funding or conflicts of interest to disclose.

© 2012 Lippincott Williams & Wilkins, Inc.