Presenter’s name (Last, First): Briggs, Gabrielle

Qualifications: PhD

Affiliations: School of Medicine and Public Health, University of Newcastle

Other authors:
Scott Gelzinnis, Simone Meakes, Kate King, Zsolt Balogh

Email: gabrielle.briggs@newcastle.edu.au

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Background / Introduction:
Bacteraemia in trauma patients can lead to fracture related infections (FRI). Screening for bacteraemia prior to ORIF surgery is not routine, due to the time limitation of cultures, the limited specificity of inflammatory markers and clinicians’ reliance on the presumed efficacy of prophylactic antibiotics. A tool for identifying bacteraemic patients prior to planned internal fixation in polytrauma patients could allow the optimal timing of surgery to prevent FRI and the associated dismal outcomes.

Patients / Methods:

We measured circulating bacterial DNA using 16SRNA qPCR as an indicator of bacteraemia. Blood samples were collected preoperatively to day 5 postoperatively from 25 trauma patients requiring pelvic, acetabular, femur or tibia/fibula ORIF surgery. Blood from 4 healthy controls was also collected. Blood plasma was further separated to cell-free and pellet fraction (including prokaryotic cell size range). DNA was extracted and bacterial DNA (bDNA) measured using 16S RNA qPCR.Average age of patients was 47±21yrs and 68% male. Median time to planned secondary surgery was 63hours. 3 patients developed postoperative multiple organ failure, 1 developed sepsis, 3 developed FRI. bDNA was not detected in any cell-free plasma samples. In the centrifuged pellet fraction, bDNA was detectable in all samples, including healthy controls (preop trauma 0.31 (0.22-0.69)ng/mL, healthy 0.72 (0.07-0.79) ng/mL. There were no differences in circulating bDNA over time postoperatively, between healthy controls and trauma patients or in those with complications. One of the 3 patients with subsequent FRI had the highest preoperative bDNA (17x greater than the median).

Results:

Average age of patients was 47±21yrs and 68% male. Median time to planned secondary surgery was 63hours. 3 patients developed postoperative multiple organ failure, 1 developed sepsis, 3 developed FRI. bDNA was not detected in any cell-free plasma samples. In the centrifuged pellet fraction, bDNA was detectable in all samples, including healthy controls (preop trauma 0.31 (0.22-0.69)ng/mL, healthy 0.72 (0.07-0.79) ng/mL. There were no differences in circulating bDNA over time postoperatively, between healthy controls and trauma patients or in those with complications. One of the 3 patients with subsequent FRI had the highest preoperative bDNA (17x greater than the median).

Conclusion:

We demonstrated that high-speed centrifugation allows circulating bDNA detection in orthopedic trauma patients and that surgery does not increase bDNA. Future studies would benefit from this step to concentrate bDNA for both quantitation/downstream microbiome profiling. Larger studies are required to determine the predictive/diagnostic utility of bDNA load in timing surgery.

Level of Evidence & Study type: Level III

Declarations of Conflict: No conflicts of interest