Microbiology of unresolved bone infection: is it recurrence or recalcitrance?

Abstract

Background: Bone infections are dreaded complications and remain a challenge for orthopaedic surgeons. Unresolved bone infection is caused by a broad spectrum of microorganisms; however, a few microorganisms persist from the initial infection. There are no published series reporting the microbiology in unresolved bone infection in low- or middle-income countries. This study aims to review the recurrence and recalcitrance of microorganisms in unresolved bone infection in the South African setting.

Methods: A single-centre retrospective cohort study reviews patients who underwent revision eradication surgery for unresolved bone infection between June 2016 and March 2023. Recalcitrance of bone infection was defined as the persistence of the same species of pathogen isolated at the time of index eradication surgery for bone infection. Recurrence was defined as a change in pathogen profile at the time of revision infection eradication surgery.

Results: Eleven patients had unresolved bone infections following eradication surgery. There were eight males and three females, with a mean age of 43.27 years (± 12.64 SD, range 25–58). The anatomical sites most frequently affected were the tibia (6/11, 55%) and femur (3/11, 27%). There is no statistically significant difference in the number of single species yielded (p = 0.586), polymicrobial species yielded (p = 1.0) or negative yield (p = 0.635) at secondary surgery. There is no similarity in the distribution of microorganisms at index surgery and secondary surgery. The causative pathogen for cases of unresolved bone infection had a higher probability to be different from the initial isolate obtained at the time of index surgery (73%), representing recurrence rather than persistence of the original infection.

Conclusion: This study reported a higher probability of encountering different species of microorganisms at secondary surgery as opposed to the recurrence of similar species. The culture obtained at index surgery is not a reliable predictor of microorganisms involved in unresolved bone infection. Therefore, new deep specimens are always required to determine the causative microorganism of unresolved bone infection.

Level of evidence: 4