Destructive Erysipelothrix rhusiopathiae Endocarditis Confirmed on Valve Tissue Culture After Persistent Blood...

Erysipelothrix rhusiopathiae is a zoonotic, gram-positive bacillus that is a virulent cause of infective endocarditis (IE) and incurs a high mortality rate. Its virulence is compounded by intrinsic resistance to common empirical agents including vancomycin and aminoglycosides. Given it is historically associated with a high rate of bacteraemia, its presentation in this case report as blood culture-negative but tissue culture positive infective endocarditis is highly uncommon. We report the case of an immunocompetent female in her 60s with relevant environmental exposure presenting with acute heart failure. Later determined to be secondary to highly destructive, native IE confirmed on transesophageal echocardiography (TOE). Despite the significant burden of disease, three sets of blood cultures collected during a period without antibiotic treatment remained persistently negative. The patient underwent urgent mechanical aortic valve replacement. With the definitive diagnosis only being established post-operatively after culture of the excised aortic valve tissue yielded E. rhusiopathiae. Following identification and susceptibility testing, antibiotic therapy was rationalized to 4 weeks of intravenous benzylpenicillin monotherapy, resulting in clinical recovery. This case highlights the rare but significant presentation of E. rhusiopathiae IE underscoring the critical role of advanced tissue diagnostics in high-burden, culture-negative endocarditis. Further, this case reinforces the need for clinicians to maintain a high index of suspicion for this organism in patients with relevant environmental exposures, ensuring timely initiation of appropriate antibiotic regimens particularly given its intrinsic resistance to commonly used empirical endocarditis therapies.