Uncertainty of Treatment of Serratia marcescens Endocarditis

Aim: To discuss two patient cases of Serratia marcescens endocarditis and the paucity of literature regarding treatment options.

Presentation of Case: Patient 1 was a 29-year old male who presented with native mitral valve Serratia marcescens endocarditis presumed secondary to intravenous drug use. He was empirically treated with vancomycin and piperacillin/tazobactam then transitioned to meropenem and gentamicin 1 mg/kg every 8 hours. He was maintained on vancomycin monotherapy for days 4-14. Gentamicin was restarted on hospital day 14 at 7 mg/kg every 36 hours for 6 weeks. He underwent mitral valve replacement on hospital day 20. He was readmitted on day 42 with splenic lesions and enlarging mycotic aneurysms. Patient 2 was a 38-year old male with native aortic valve Serratia marcescens endocarditis with septic emboli presumed secondary to intravenous drug use. He was treated with vancomycin and cefepime then was transitioned to ceftriaxone and levofloxacin. The patient underwent aortic valve replacement on hospital day 3 and was transitioned to meropenem and levofloxacin for 6 weeks.

Discussion: The treatment strategies for both patients demonstrates that the optimal treatment strategy for Serratia marcescens endocarditis remains unclear. The gentamicin dosing for patient 1 demonstrates “synergy” and extended-interval dosing. Despite both dosing strategies being used, the patient continued to exhibit complications of the infection. Patient 2 demonstrates successful treatment of the infection with surgical intervention and a carbapenem/fluoroquinolone regimen.

Conclusion: These cases demonstrates that much remains unclear in the treatment of Serratia marcescens endocarditis and more studies and case reports are needed.