Normal procalcitonin, C-reactive protein, and negative blood cultures in infective endocarditis with a massive residual vegetation: a case report

BACKGROUND: Infective endocarditis (IE) is a serious infection with high morbidity and mortality that involves the endocardial lining of the heart. Most cases of IE are due to bacteria although other atypical micro-organisms can also be involved. Procalcitonin (PCT) is a biomarker that is used in the diagnosis of bacterial infections. CASE SUMMARY: We present the case of a 54-year-old patient with bacterial endocarditis who has been regularly visiting his cardiologist for follow-up on a mitral valve prolapse and moderate mitral regurgitation (MR) for the last 11 years. During his last visit, transthoracic echocardiography (TTE) showed a previously non-existent structure on the posterior mitral valve leaflet with severe MR. Blood cultures were positive for Streptococcus viridans. On admission, he had elevated levels of PCT and C-reactive protein which returned to normal values after 4 weeks of intravenous antibiotic therapy. His follow-up blood cultures, taken after normalization of PCT, did not show bacterial growth; however, on TTE he had severe mitral regurgitation and a persistent vegetation which had slightly increased in size after completion of the full antibiotic course. He was referred for mitral valve replacement surgery. DISCUSSION: Normalization of procalcitonin levels may correlate with negative blood cultures in cases of IE with residual vegetations. The optimal time for surgery in such patients is difficult to define but even in circumstances with less infective organisms such as S. viridans and late in the course of the disease residual vegetations remain a serious risk factor for embolic events. Randomized controlled clinical trials are needed in order to have better recommendations with solid evidence regarding prophylaxis and treatment in IE.