Detection of Pathogenic Bacteria from Septic Patients Using 16S rRNA gene Targeted Metagenomic Sequencing.

BACKGROUND Conventional blood cultures were compared to plasma cell-free DNA-based 16S ribosomal RNA gene PCR/next generation sequencing (16S rRNA gene NGS) for detection and identification of potential pathogens in septic patients. METHODS Plasma was prospectively collected from 60 adult patients with sepsis presenting to the Mayo Clinic (Minnesota) Emergency Department from March through August 2019. Results of routine clinical blood cultures were compared to those of 16S rRNA gene NGS. RESULTS 19 (32%) subjects had positive blood cultures, of which 13 yielded Gram-negative bacilli, 5 Gram-positive cocci and one both Gram-negative bacilli and Gram-positive cocci. 16S rRNA gene NGS findings were concordant in 11. For the remaining 8, 16S rRNA gene NGS results yielded discordant detections (n=5) or were negative (n=3). Interestingly, Clostridium species were additionally detected by 16S rRNA gene NGS in 3 of the 6 subjects with gastrointestinal sources of Gram-negative bacteremia and none of the 3 subjects with urinary sources of Gram-negative bacteremia. In the 41 remaining subjects, 16S rRNA gene NGS detected at least one potentially pathogenic organism in 17. In 15, the detected microorganism clinically correlated with the patient's syndrome. In 17 subjects with a clinically defined infectious syndrome, neither test was positive; in the remaining 7 subjects, a non-infectious cause of clinical presentation was identified. CONCLUSION 16S rRNA gene NGS may be useful for detecting bacteria in plasma of septic patients. In some cases of Gram-negative sepsis, it may be possible to pinpoint a gastrointestinal or urinary source of sepsis based on the profile of bacteria detected in plasma.