16S rDNA PCR for the aetiological diagnosis of culture-negative infective endocarditis.

INTRODUCTION: Culture-negative infective endocarditis (IE) accounts for 7-31% of all cases. Metagenomics has contributed to improving the aetiological diagnosis of IE patients undergoing valve surgery. We assessed the impact of 16S ribosomal DNA gene polymerase chain reaction (16S rDNA PCR) in the aetiological diagnosis of culture-negative IE.

METHODS: Between January 2016 and January 2020, clinical data from culture-negative IE patients were reviewed retrospectively. Identification of bacteria was performed using 16S rDNA PCR in heart valve specimens.

RESULTS: 36 out of 313 patients (12%) with culture-negative IE had their valve tissue specimens submitted for 16S rDNA PCR. 16S rDNA PCR detected and identified bacterial nucleic acid in heart valve tissue significantly more frequently compared to valve culture alone 25(70%) vs 5(12%); p < 0.05. Mean age was 57 years (SD 18) and 80% were male. Native and aortic valve were involved in 76% and 52% of cases, respectively. Streptococcus spp. (n 15) were the most commonly detected organisms, followed by bacteria of the HACEK group (Haemophilus parainfluenzae 2, Aggregatibacter actinomycetemcomitans 1), nutritionally variant streptococci (Abiotrophia defectiva 2), and one each of Staphylococcus aureus, Corynebacterium pseudodiphtheriticum, Helcococcus kunzii, Neisseria gonorrhoeae, Tropheryma whipplei.

CONCLUSION: 16S rDNA PCR may be a useful diagnostic tool for the identification of the causative organism in culture-negative IE. Efforts towards a shorter turnaround time for results should be consider and further studies assessing the clinical impact of this technique in culture-negative IE are needed.