Mycobacterium abscessus: A Rare Cause of Periprosthetic Knee Joint Infection

DISCUSSION

Diagnosis of acute infection after TKA remains challenging, as some degree of pain, swelling, and even postoperative fevers may be common in noninfected TKA patients. Synovial white blood cell count and differential as well as alpha-defensin levels have been cited as predictive factors of infection.^16,17 Deep tissue and synovial fluid cultures offer the advantage of both identification and antimicrobial sensitivity testing of the offending organism. In this case, culture of the knee joint fluid at the time of TKA led to the unexpected finding of M. abscessus infection.

Preventable outbreaks due to M. abscessus have been reported and attributed to contaminated multiuse instruments, inadequate sterilization of tap water, multiuse vials, and improper skin preparation.^11-13 Rarely, M. abscessus has been reported as the cause of PJI. When an unusual organism is encountered after native joint instrumentation, an investigation should be undertaken to identify the source of contamination, with the assistance of infection control practitioners and/or the US Food and Drug Administration reporting. Reporting and investigation was undertaken in this case, though no suspect source could be identified.

Although there were no signs of infection prior to the TKA, there is an ongoing debate as to whether intra-articular corticosteroid injections increase the risk of PJIs, and if so, what the optimal amount of time to wait between procedures is. Although several earlier studies have been underpowered to answer these questions,¹⁸ this patient underwent TKA 1 month following the corticosteroid injection. Recent meta-analyses have shown no definitive evidence to indicate that this increased her risk of PJI.^19,20

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