Heart valve culture and sequencing to identify the infective endocarditis pathogen in surgically treated patients

Background: Testing excised valves in surgically treated infective endocarditis (IE) patients provides an opportunity to identify the microbial etiology of IE. Microbial sequencing (universal bacterial, mycobacterial, or fungal polymerase chain reaction followed by DNA sequencing) of valves can identify microorganisms accurately, but the value it adds beyond information provided by blood and valve cultures has not been adequately explored.

Methods: Three hundred fifty-six patients who underwent surgery for active IE from January 1, 2010, to January 1, 2013, were identified from our cardiovascular information registry and outpatient parenteral antibiotic therapy registry. Their records were reviewed to identify 174 patients whose valves were sent for sequencing. The microbial etiology of IE was defined using comprehensive clinical, pathologic, and microbiological criteria. Blood culture, valve culture, and valve sequencing were examined to determine how frequently they identified the definitive cause of IE.

Results: Of the 174 patients, 162 (93%) had acute inflammation on histopathologic examination of their valves. Valve sequencing was significantly more sensitive than valve culture in identifying the causative pathogen (90% versus 31%, p < 0.001), and yielded fewer false positive results (3% versus 33%, p <0.001). The pathogen would not have been identified in 25 patients (15%) had it not been for valve sequencing. All the value provided by sequencing was attributable to bacterial DNA sequencing; mycobacterial and fungal sequencing provided no additional information beyond that provided by blood culture, histopathology, and valve culture.

Conclusions: Valve sequencing, not valve culture, should be considered the primary test for identifying bacteria in excised cardiac valves.