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    Novel Method of Isolating Infecting Organisms after Joint Replacement Surgery

    Current diagnostic practices can fail to detect the bacteria causing a periprosthetic joint infection (PJI) in 30% to 50% of clinical cases, complicating or delaying appropriate treatment.

    Researchers from Thomas Jefferson University in Philadelphia, Pennsylvania, have found that genomic analysis using next-generation sequencing (NGS) can identify infecting organisms in more than 80% of cases of PJIs that had previously escaped detection. Their findings were recently published in The Journal of Bone & Joint Surgery.

    “This method can help detect pathogens that we would otherwise miss using standard approaches, namely culture,” said senior author Javad Parvizi, MD, Vice Chairman of Research and Professor of Orthopedic Surgery at The Rothman Institute at Thomas Jefferson University. “The study has revealed unexpected pathogens and led us to select more appropriate and effective treatments for patients.”

    To test the ability to isolate infective organisms, Dr. Parvizi and colleagues prospectively enrolled patients undergoing a revision joint replacement procedure over a 9-month period in 2016, and then assessed for organisms identified using traditional method: culture, side by side with NGS.

    The results showed that NGS identified organisms in 89% of infected patients versus 61% with culture. Furthermore, NGS was able to detect the pathogen in 81% of patients who had tested negative for pathogens by the standard culture method.

    One patient, whose case was described in a separate paper in Arthroplasty Today, presented at the emergency department with a PJI. Although standard culture was unable to identify the pathogen, NGS diagnostic tests resulted in an unexpected finding: The infection was caused by Streptococcus canis, an organism found in dogs. Further questioning of the patient confirmed that he had been scratched by his dog a few days prior to the joint infection. Once the pathogen was known, the patient could be switched to more effective antibiotics and he recovered well.

    “The fact that we can use this technology to detect organisms in culture-negative patients with an infected prosthesis may be significant, and it could help us provide targeted treatment for these patients,” said co-author Karan Goswami, MD, a research fellow and PhD candidate affiliated with The Rothman Institute at Jefferson.

    “However, further study is required to validate our findings in larger numbers and determine the significance of NGS signal on treatment outcomes. A multicenter trial is underway to explore this question.”

    The American Academy of Microbiologists (AAM) recently published a report supporting the use of NGS, stating that, “…NGS has the potential to dramatically revolutionize the clinical microbiological laboratory by replacing current time-consuming techniques with a single all-inclusive diagnostic test.”

    “Because of its promising role in diagnosing patients with periprosthetic joint infection, we have already begun to use the genomic test at our institution to isolate organisms in patients with suspected joint infection,” Dr. Parvizi said “NGS has provided critical information for the management of cases of periprosthetic joint infection at our institution, and we work closely with our microbiology colleagues to optimize treatment for these patients.”

    Sources

    M Tarabichi, Shohat N, Goswami K, et al Diagnosis of periprosthetic joint infection: the potential of next-generation sequencing. J Bone Joint Surg Am 2018 Jan 17;100(2):147-54.

    M Tarabichi, Alband A, Shohat N, Goswami K, Parvizi J. Diagnosis of streptococcus canis periprosthetic joint infection: the utility of next-generation sequencing, Arthroplasty Today. Published online ahead of print October 13, 2017.

    Disclosures

    Dr. Parvizi has disclosed that he has ownership interest in MicroGenDX, the laboratory that provided next-generation sequencing of samples in this study. No other authors reported disclosures relevant to this study.