Evaluation of a commercial 16S rDNA PCR assay (UMD-SelectNA, Molzym) for pathogen detection from cardiac tissue specimens

The detection of bacteria in cardiac tissue, vegetations, or explanted prosthetic valves using nucleic acid amplification tests, such as 16S rDNA amplicon sequencing (16S rDNA PCR), has been incorporated as pathologic criterion for definite infective endocarditis into the 2023 Duke-International Society for Cardiovascular Infectious Diseases Criteria for Infective Endocarditis. To verify results from previous studies suggesting increased detection rates and to investigate the added diagnostic value of 16S rDNA PCR, we prospectively compared the diagnostic yield of a CE-IVD-marked 16S rDNA PCR assay to conventional culture (CC) in a large number of cardiac tissue samples, relating our findings to microbiological evidence from blood culture sampling and patient history. Over a seven-year period (2016-2023), 687 cardiac tissue samples were subjected to CC and 16S rDNA PCR. 16S rDNA PCR and CC yielded positive results in 326 (47.4 %) and 154 (22.4 %) samples, respectively. 136 (19.7 %) samples were concordantly tested positive. In 190 (27.7 %) and 18 (2.6 %) samples, a positive result was obtained only by PCR or CC. 343 (49.9 %) samples tested negative by both methods. In a case-based analysis of a subgroup of blood culture-confirmed IE (241 cases) and BC-negative non-IE cases (126 cases), 16S rDNA PCR yielded a diagnostic sensitivity and specificity of 74.7 % and 98.4 %, while CC yielded a sensitivity and specificity of 38.6 % and 99.2 %. In conclusion, the use of 16S rDNA PCR significantly increased the detection rate for bacteria in heart valve tissue. A notable proportion of the culture-negative samples contained pathogens that are generally not detectable by conventional culture. Therefore, supplementation of CC with 16S rDNA PCR is recommended for cardiac tissue samples, especially in case of blood culture-negative endocarditis.