AGAINST THE NATIVE JOINT MICROBIOME: UNIFORMLY NEGATIVE NGS IN HIP SYNOVIAL FLUID WITH PAIRED SALINE CONTROLS

Introduction Humans exist in an intricate symbiotic relationship with host microbiome populations. It has been recently reported using Next Generation DNA Sequencing (NGS), that a native synovial joint microbiome may exist potentially contributing microbes in clinical infection. The counter argument is that synovial joints are sterile and positive detection reflects errant sampling and processing. We evaluate native hip synovial fluid sampled via a low-risk air-excluding technique incorporating paired saline controls and stringent NGS quality thresholds. Methods In this prospective cohort study, 40 consecutive patients undergoing primary Total Hip Arthroplasty (THA) for osteoarthritis were enrolled. All hips were approached via a posterolateral approach. Upon arthrotomy, hip fluid was directly aspirated with an 18-gauge needle into a 10cc syringe. Technique was meticulous not to aspirate any air. A concomitant control specimen was obtained by aspirating sterile saline from a freshly opened 100cc container on the operative field using an identical technique. All fluid aspirates were transferred into DNA-specific sterile vacutainers and sent overnight for NGS analysis. Results 40 hips were sampled, with one control specimen not sent with its corresponding test specimen. 16 hips were male (40%) and mean age was 67 years (range 41–89). All 40 synovial fluid specimens showed no significant DNA reads. All 39 saline control specimens showed no significant DNA reads. Conclusion Intraoperative NGS of 40 consecutive hip synovial fluid samples and all paired saline controls was uniformly negative using an air-excluding sampling technique, arguing against the existence of a native joint microbiome, a finding consistent with the teleologic principle of immunologic parsimony.