The diagnostic benefit of 16S rDNA PCR examination of infective endocarditis heart valves: a cohort study of 146 surgical cases confirmed by histopathology

Abstract

Aims: Upon suspicion of infective endocarditis, the causative microorganism must be identified to optimize treatment. Blood cultures and culturing of removed valves are the mainstay of this diagnosis and should be complemented by growth-independent methods. We assessed the diagnostic benefit of examining removed endocarditis valves by broad-range bacterial PCR to detect causative bacteria in cases where culturing was not available, negative, or inconclusive because a skin commensal was detected, in patients from our clinical routine practice.

Methods and results: Patients from Heidelberg University Hospital with suspicion of endocarditis, followed by valve replacement and analysis by 16S rDNA PCR, between 2015 and 2018, were evaluated. 146 patients with definite infective endocarditis, confirmed by the valve macroscopics and/or histology, were included. Valve PCRs were compared to corresponding blood and valve culture results. Overall, valve PCR yielded an additional diagnostic benefit in 34 of 146 cases (23%) and was found to be more sensitive than valve culture. In 19 of 38 patients with both negative blood and valve cultures, valve PCR was the only method rendering a pathogen. In 23 patients with positive blood cultures detecting skin commensals, 4 patients showed discordant valve PCR results, detecting a more plausible pathogen, and in 11 of 23 cases, valve PCR confirmed commensals in blood culture as true pathogens. Only the remaining 8 patients had negative valve PCRs.

Conclusion: Valve PCR was found to be a valuable diagnostic tool in surgical endocarditis cases with negative blood cultures or positive blood cultures of unknown significance.

Trial registration: S-440/2017 on 28.08.2017 retrospectively registered. Subdividing of all infective endocarditis patients in this study, showing that valve PCR yields valuable information for patients with skin commensals in blood cultures, which were either confirmed by the same detection in valve PCR or refuted by the detection of a different and typical pathogen in valve PCR. Additionally, benefit was determined in patients with negative or not available blood cultures and only positive detection in valve PCR. +: Positive; -: negative; n/a: not available results.

Keywords: Heart valve; Infective endocarditis; PCR; Pathogen detection; Skin commensal.

Fig. 1

a Flowchart of infective endocarditis (IE) patients with microorganism detection. b Venn diagram comparing detection by each microbiological method. +: Positive; −: negative results

Fig. 2

a Flowchart of microorganism detections by valve PCR and blood cultures. b Distribution of microorganisms detected by valve PCR; blood cultures are concordant or different compared to valve PCR or inconclusive, negative or not available. +: Positive; −: negative; n/a: not available results

Fig. 3

Flowchart of infective endocarditis (IE) patients with diagnostic benefit from valve PCR, shown by red box and detailed in Table 3 under the corresponding letters. +: Positive; −: negative; n/a: not available results; ^amarks patients with the difference between blood culture and valve PCR, also in Table S2; ^bmarks 7 patients with negative valve PCRs and 1 case with eubacterial DNA in PCR, but unsuccessful species identification; in all 8 patients valve culture remained negative