PCR-electrospray ionization mass spectrometry for direct detection of pathogens and antimicrobial resistance from heart valves in patients with infective endocarditis

Microbiological diagnosis is pivotal to the appropriate management and treatment of infective endocarditis. We evaluated PCRelectrospray ionization mass spectrometry (PCR/ESI-MS) for bacterial and candidal detection using 83 formalin-fixed paraffinembedded heart valves from subjects with endocarditis who had positive valve and/or blood cultures, 63 of whom had positive valvular Gram stains. PCR/ESI-MS yielded 55% positivity with concordant microbiology at the genus/species or organism group level (e.g., viridans group streptococci), 11% positivity with discordant microbiology, and 34% with no detection. PCR/ESI-MS detected all antimicrobial resistance encoded by mecA or vanA/B and identified a case of Tropheryma whipplei endocarditis not previously recognized.