Summary

Polymicrobial endocarditis is a rare clinical entity associated with high rate of morbidity and mortality. We present a case of prosthetic valve endocarditis caused by Enterococcus faecalis and Proteus mirabilis, emphasizing the clinical course, microbiological findings, and potential microbial synergy contributing to disease persistence.

E. faecalis is a gram-positive, facultatively anaerobic bacterium that can cause significant morbidity and mortality. It commonly presents as bacteremia and endocarditis and is a major contributor to nosocomial infections. This bacterium produces biofilms on native and artificial tissues, allowing it to establish resistance to antimicrobial agents. Many infections caused by E. faecalis are polymicrobial, as its biofilm creates an environment that supports the colonization of other microorganisms, leading to mixed-species biofilms on endogenous tissues or medical devices.