Fatal Streptococcus viridans ( S. oralis) aortic prosthetic valve endocarditis (PVE) with paravalvular abscesses related to steroids

Abstract

Streptococcus viridans (ie, the viridans Streptococci) is a term for avirulent, noninvasive, commensals whose primary habitat is the oral pharynx. Because of their lack of virulence and invasive potential, S. viridans virtually causes only subacute endocarditis (SBE). To cause SBE, the viridans streptococcal species require a damaged endothelium and heart valve to adhere to for the infectious process to be initiated. The frequency distribution of viridans streptococcal strains associated with SBE is directly related to their ability to produce capsule important for adherence. Strains with capsules are more frequently associated in SBE than those species with less abundant capsules. Viridans streptococci rarely cause native prosthetic valve endocarditis (PVE). Clinically, SBE caused by viridans streptococci is characterized by temperatures of less than 102°F with a cardiac murmur and may be accompanied by splenomegaly and peripheral manifestations. S. viridans SBE rarely results in valvular destruction or perivalvular abscesses. In contrast, acute bacterial endocarditis caused by virulent pathogens (eg, Staphylococcus aureus) is capable of infecting and destroying normal heart valves and is often accompanied by congestive heart failure, septic emboli, and perivalvular abscess and leaks. PVE may involve mechanical or bioprosthetic valves and clinical presentation, and the severity depends on the pathogen and number of valves affected. The clinical course of PVE caused by relatively avirulent pathogens resembles SBE caused by viridans streptococci. There are little data on the untoward effects of steroids in patients with S. viridans SBE. We present a case of aortic PVE caused by S. oralis ,a viridans streptococcus, treated with steroids. Postmortem examination revealed aortic prosthetic valve involvement with two large periaortic valvular abscesses and a large perivalvular leak that, despite appropriate antibiotic treatment, led to the patient’s precipitous demise. We believe this is the first reported case of fatal aortic valve PVE caused by S. oralis related to steroids. Subacute bacterial endocarditis (SBE) refers to a