Mycobacterium abscessus subsp. massiliense infection secondary to traumatic anterior cruciate ligament reconstruction surgery

Postoperative anterior cruciate ligament (ACL) reconstruction infections are rare, with postoperative infection rates ranging from 0.14-2.6% [1]. The causative microorganisms are typically part of the normal skin flora, Non-tuberculous Mycobacterium (NTM) infections following knee surgery are rarely reported in the literature. One month after arthroscopic lysis of adhesions from anterior cruciate ligament (ACL) reconstruction, a 67-year-old male patient presented with symptoms suggesting septic arthritis. Empiric antibiotics were initiated. Intraoperative cultures were positive for Mycobacterium abscessus. Organismspecific antimicrobial therapy with azithromycin, amikacin, and imipenem were started. Four months later the patient was switched to oral outpatient treatment with azithromycin, clofazimine and bedaquiline. Mycobacterium infections following ACL reconstruction are exceedingly rare in the United States. Successful management of Mycobacterium abscessus infection is exceptionally challenging for both orthopedists and infection disease specialists.


Coagulase-negative Staphylococci and
Staphylococcus aureus comprising nearly 90% of the cases [2]. Graft choice may be associated to the risk of infection with a reported increased risk for hamstring tendon (HT) compared to bone-patellar tendon-bone (BPTB) autograft [3] and for allografts compared to autografts [4].

Mycobacterium infections
following ACL reconstruction are rare, with rates of Mycobacterium tuberculosis infection following ACL reconstruction estimated to be 0.68% in immunocompetent individuals [5]. Nontuberculous Mycobacterium (NTM) infections following knee surgery are also rarely reported in the literature [6,7]. Herein, we present a case of Mycobacterium abscesses following ACL reconstruction surgery.  Figure 2). Intraoperatively, 15mL of purulent joint fluid was obtained and sent for cultures ( Figure  2). Intraoperative cultures were positive for Mycobacterium abscessus subsp. Massiliense, as we routinely test for NTM species in knee sepsis cases. The isolate was sensitive to amikacin and clarithromycin, tentatively sensitive to azithromycin and tigecycline and clofazimine, and intermediate to cefoxitin and imipenem. Organismspecific antimicrobial therapy with azithromycin (500mg PO daily), Amikacin (10mg/kg IV daily) and imipenem (500mg every 8h.) was started. Clinical improvement with resolution of fever, warmth, and erythema soon followed.

Case report
One month after surgery, MRI demonstrated a partially retained tibial interference screw, decreased effusion, synovial thickening, enhancement, and adjacent periosteal reaction, especially posterior to the distal femur and in the suprapatellar recess ( Figure  3).  The bone marrow edema and corresponding confluent low T1 signal within the anterior tibia and adjacent to the tibial tunnel appeared to be worse than the MRI done one month prior and was concerning for ongoing osteomyelitis. On month after surgical irrigation, the patient underwent removal of the partially retained tibial screw, irrigation, and tunnel reaming/debridement ( Figure  4). Specimens sent for Mycobacterium PCR and acid-fast bacilli cultures were negative.
In addition, he was continued on azithromycin (500mg daily), the amikacin was switched to tigecycline (50 mg IV every 12h) after he developed ototoxicity from the amikacin and the imipenem was narrowed to cefoxitin (3g IV every 8hrs.). Three months after removal of tibial screw and tunnel reaming the cefoxitin was discontinued after he developed a generalized rash associated with eosinophilia (18.7%) and he was kept on azithromycin and tigecycline.
As of recent, the patient displayed range of motion of 5-110 degrees at their follow up visit two months after cefoxitin was discontinued he was switched to a complete oral antibiotic that included azithromycin, clofazimine and bed aquiline. This regimen was continued for 7 months after which the patient returned to our clinic having ceased all anti-biotic treatment and continued to progress through our standard rehabilitation protocol.

Figure 4:
Sagittal proton density fat suppressed MRI demonstrates interval removal of the previously seen tibial tunnel interference screw (orange arrow) since the prior study ( figure 3). There remains the ACL Swivelock anchor (red circle), which may serve as a nitus for infection. Peri-articular soft tissue edema is still present but improving compared to previous imaging (red arrow and blue arrow).

Discussion and Conclusion
Mycobacterium infection following ACL reconstruction is rare. Nag et al. [5] reported a series of eight M. Tuberculosis