Nontuberculous mycobacteria include a range of species not often encountered in the hospital environment; therefore, their treatment and appearance may not be easily identified. Among these species is Mycobacterium chelonae , a highly drug-resistant pathogen that is found in freshwater, degraded solutions, and even some aquatic animals. Like other species in this genus, combating it is difficult not only due to its unlikely presence but also being impermeable to many detergents commonly used.

M. chelonae infections often have no defining feature, resembling many common infections. The most common manifestation of M. chelonae is skin and soft tissue invasion, causing cellulitis, blistering, and pustules. ^,, Furthermore, being opportunistic, chronic wounds and surgical sites have been known to be complicated by M. chelonae . Although the aforementioned superficial appearance of these infections is most common, deeper infiltration of M. chelonae has been documented. In some instances, infections caused by M. chelonae are seeded in catheters and cause vertebral osteomyelitis. The non-pathognomonic appearance and benign findings of this bacterium in these wounds make clinical suspicion for non-tuberculosis mycobacteria lower, which could further delay accurate diagnosis and ultimately treatment. Treatment for osteomyelitis caused by M. chelonae involves a minimum of 6 months of antibiotics guided by clinical improvement; however, “aggressive management” involves antibiotic therapy for 6–12 months with the addition of surgical intervention.

M. cholenae infections of the foot and ankle are rare, with only a few case reports in the literature. Some cases share the similarity of being associated with complications, including tenosynovitis and osteomyelitis, arising during the post-surgical period, which include the talus and Achilles tendon, while other reports document osteomyelitis of the first metatarsal, medial, and lateral malleolus in the absence of trauma or surgery. ^,,, Of these reports, osteomyelitis of the foot and ankle was noted to be rare, with the most successful outcome necessitating serial debridement along with long-term antibiotic therapy.

In this case report, we detail a patient who experienced recurrent hospitalizations for over a year involving multiple podiatric, orthopedic, and vascular surgical interventions and was found to have a disseminated Mycobacterium chelonae infection in the left foot and left hand. Unfortunately, while the patient was being treated with antibiotics and debridement, the patient began to decompensate and eventually succumbed to his multiple comorbidities.

A 78-year-old male with a past medical history of COPD, hypertension, CAD s/p CABG and atrial flutter s/p permanent pacemaker was hospitalized in late July 2023 due to septic shock in the presence of right lower leg cellulitis/tenosynovitis and was found to have discharge from a right heel wound. After consultation to podiatric surgery and recommendation of advanced imaging, magnetic resonance imaging (MRI) showed multiple bone lesions in the distal tibia and fibula, posterolateral calcaneus, anterior calcaneus and head of the talus with “associated endosteal scalloping, cortical thinning and bone in the medial malleolus and fibula with fluid collection along the lateral aspect of the hindfoot extensions into kager’s triangle”. Deep wound cultures were negative for the right foot wound (the original consultation), and no surgical intervention was done during this admission due to patient refusal. Under the guidance of the hospital’s infectious disease (ID) department, the patient was discharged on unasyn for four weeks.

The patient returned a little over 1 month later to the hospital with complaints of new right foot and ankle swelling. Fluctuance was noted over the midfoot, and a bedside incision and drainage was conducted with the eventual expression of purulence, growing no organisms. At the same time, a blister was noted on the patient’s lateral aspect of the left foot, which was de-roofed, and purulence was cultured; the patient was started on vancomycin and zosyn per ID input. While in the hospital, the patient’s right ankle and foot became more erythematous and edematous, requiring another incision and drainage bedside with purulence expressed. Another MRI was obtained, which demonstrated osteomyelitis of the entire 1st metatarsal with multiple intraosseous abscesses in the first interspace with rim-enhancing abscess in the plantar foot near the peroneus longus, osteomyelitis of the 5th proximal phalanx and metatarsal head, and rim-enhancing collections near the 5th extensor tendon of the right foot. Although another attempt for surgical intervention was offered, given the findings of the right foot, this was put on hold as noninvasive vascular testing and arterial imaging demonstrated concern for reduced perfusion of the bilateral extremities. It was deemed necessary to attempt to revascularize the right lower extremity by vascular colleagues before management of the right foot osteomyelitis. Vascular surgery conducted a right common femoral-SFA endarterectomy, a right common iliac artery stent, and a right SFA-Popliteal stent. After this intervention, the erythema and edema regressed, and all repeat cultures were negative. The patient was discharged on six weeks of vancomycin and zosyn via a peripherally inserted central catheter.

For the next 2 months, the patient was seen in the office for wound care and transitioned from zosyn and vancomycin to augmentin due to PICC issues. He was seen back in the hospital for issues unrelated to his wounds at this time; however, the wounds appeared to be worse. New MRI findings of the right foot and ankle showed enhancing lesions of the distal tibia and fibula, calcaneus, talus, first metatarsal, third middle phalanx, 5th proximal phalanx, and 5th metatarsal head, with the previous fluid collection near Kager’s triangle decreased. Since the left foot clinically worsened with wounds probing to bone, an MRI was also ordered. The MRI exhibited enhancing lesions of the 5th metatarsal with bone lesions and fracturing of the 5th metatarsal head and lesions of the 3rd proximal middle phalanx, cuboid, lateral and intermediate cuneiform, as well as the anterior calcaneus with fluid collection along the dorsal aspect of the 5th distal metatarsal. Of note, at this same time, the cutaneous lesions and wounds of the patients’ left upper extremity warranted an MRI of the left hand, which noted osteomyelitis of the distal aspect of the 4th proximal phalanx and fluid collection of the index finger. As the patient’s primary concern in the hospital was not the wounds at this time, he was discharged and restarted on antibiotics consisting of augmentin and doxycycline for previous coagulase-negative staph blood cultures by ID.

The patient was seen once more in the hospital with complaints of left foot swelling and was started on zosyn. Due to the deterioration of the patient’s wounds and the patient being amenable, it was deemed necessary to then take the patient for a right ankle incision and drainage, bilateral foot and left ring finger bone biopsies. With slight improvement after the first procedure, the patient was taken back to the OR a couple of days later for closure of the previous I&D sites with a left 2nd digit arthroplasty. It should also be noted that at this time, the patient began having more cutaneous lesions noted on the left upper and lower extremities, and biopsies conducted by dermatology were negative. With clinical improvement, pathology report, and microbiology specimens showing no growth at the time, it was determined the patient was safe for discharge with six weeks of zosyn while awaiting culture results.

From the over 16 cultures taken from the feet and left finger, the left foot third middle phalanx and left ring finger grew M. chelonae, and the left second digit grew Pseudomonas aeruginosa and Enterococcus faecalis . Interestingly, and for reasons unknown, it was not until 2 weeks after the cultures were taken that these findings were acted upon and specific antibiotics were initiated: tigecycline, tobramycin, azithromycin, and ciprofloxacin by ID recommendations.

After one month of the positive previous cultures, the patient presented back to the hospital due to fluid overload and respiratory distress. The patient’s previous finger and foot operative sites remained stable, and was discharged without any further surgical intervention. After discharge, the patient remained on the inpatient antibiotic regimen of IV tobramycin and tigecycline with PO ciprofloxacin and azithromycin for eight weeks.

The patient was seen once more in the emergency department 2 weeks after the previous discharge due to having episodic diarrhea, anorexia, hypotension, and weakness. The patient’s antibiotic regimen was continued except for ciprofloxacin, as M. Chelonae appeared to be resistant, and a six-week course against Pseudomonas was completed. On physical exam, the patient was noted to have a wound on the lateral aspect of the left foot that probed to the 5th metatarsal with fluctuance, eschar to the left 2nd digit, and ischemic changes to the 3rd digit and hallux, as well as a wound near the right medial ankle. MRI demonstrated similar bone marrow changes of the left forefoot and right foot, with new fluid collections near the left cuboid and increased collection of the right talus and calcaneus. A bedside incision and drainage were done on the left lateral foot with purulence that eventually grew P. acnes . Due to the patient’s AKI, tobramycin was discontinued, and moxifloxacin was added.

Furthermore, due to the patient’s worsening vasculopathy, he underwent a left common femoral endarterectomy, stenting, and angioplasty of multiple locations of the left lower extremity before podiatric surgical intervention. Because of the irreversible ischemic changes of the left hallux 2nd digit, 3rd digit patient, and a potential new overlying infection, a transmetatarsal amputation was planned, as well as graft application to the right ankle. Vancomycin and zosyn were added to the antimicrobials. Following the left transmetatarsal amputation, the patient became dyspneic and hypoxic in the post-anesthesia care unit and was admitted to the surgical intensive care unit and intubated. Cultures taken from the TMA only grew Corynebacterium species and C. parapsilosis of the 5th metatarsal, with no more evidence of M. chelonae . The patients left TMA remained cool, most noticeably dorsal, with dusky changes, and the right ankle wound with graft remained stable.

Throughout the next week, the patient experienced an episode of cardiac arrest (requiring moxifloxacin to be stopped due to the patient’s worsening QT prolongation), worsening hemodynamics requiring multiple periods of intubation and pressor support, which lead to multiple organ failure, and a kidney injury with the need for renal replacement therapy. By family request, all vital life support systems were discontinued, and the patient expired on 3/23/23.