Mycobacterium fortuitum is a ubiquitous, rapidly growing mycobacterial species that is infrequently reported in the surgical literature. Clinically important infection with this organism has been described following trauma, injections, augmentation mammoplasty, and ultrasound hydrolipoclasia1-3. In the field of orthopaedic surgery, Mycobacterium fortuitum infection has been encountered only following prosthetic arthroplasty or fracture surgery with internal fixation4-9.
We report the case of an otherwise healthy man who underwent patellar tendon repair that was complicated by Mycobacterium fortuitum infection. While an accurate diagnosis was delayed by several weeks, aggressive surgical and specific antimicrobial therapy resulted in a favorable outcome. We emphasize the importance of surgeon awareness of this pathogen in order to facilitate accurate diagnosis and appropriate treatment.
The patient was informed that data concerning the case would be submitted for publication, and he consented.
A forty-year-old man who worked as an attorney was referred to one of us from another institution two months after surgical repair of the left patellar tendon. Three weeks before the referral, the patient had surgical wound erythema and drainage, accompanied by fever and chills. Oral cephalexin was prescribed but resulted in no improvement. Culture specimens were not obtained at that time. The medical history was otherwise unremarkable. Examination revealed that the patient was 180 cm tall and weighed 95 kg. The systemic temperature, pulse rate, and blood pressure were normal. The patient had an anterior longitudinal left knee incision with diffuse, severe surrounding erythema. The wound was open and draining, with granulation tissue exposed both proximally and in the center. The range of knee motion was from 0° to 70°. The patellar height appeared to be symmetrical on both sides, and the patient could perform an active straight leg raise. Distal motor and sensory function was normal, with normal pedal pulses. The white blood-cell count was 13,000 cells/µL, with a left shift. Magnetic resonance imaging demonstrated joint effusion, bone edema of the patella, extensive edema of the soft tissues surrounding the patella and extending toward the subcutaneous tissues, a draining sinus, and a partial to nearly-full-thickness tear of the patellar tendon (Figs. 1-A and 1-B).
With the patient under anesthesia in the operating room, pus and tissue specimens were obtained from the wound and were sent for Gram staining, bacterial culture, potassium hydroxide preparation, fungal culture, mycobacterial smear and culture, as well as histopathological analysis. At the site of the sutures that had been used for the patellar tendon repair, there was infection tracking into the patella, both at the superior aspect of the patella, where the sutures were tied at the quadriceps tendon insertion, as well as at the inferior pole of the patella, where the sutures had been passed. The wound was irrigated, the sutures were removed, and any nonviable tissue was excised. Manipulation of the knee was performed, and 120° of knee flexion was obtained. The wound was left open, and antibiotic treatment with parenteral vancomycin was initiated. Two days later, a second irrigation and débridement was performed. There was no sign of pus, and the tissue appeared to be viable and clean. As approximately two thirds of the original repair was not intact, the tear in the patellar tendon was repaired with nonabsorbable sutures. At the time of discharge to home, six days after admission, all microbiological studies were negative. A six-week course of ertapenem was prescribed for what was presumed to be a "culture-negative" infection. However, eight days after the first débridement, moderate acid-fast bacilli, which were subsequently identified as Mycobacterium fortuitum, were found on mycobacterial culture. The organism's antibiogram became available several weeks later and revealed sensitivity to aminoglycosides, clarithromycin, imipenem, fluoroquinolones, tigecycline, and trimethoprim-sulfamethoxazole. Following the course of ertapenem, the patient received six months of oral clarithromycin and trimethoprim-sulfamethoxazole. The wound healed well, and the skin sutures were removed twelve days after the second procedure. At the last follow-up visit, seven months following the operations, the patient was doing well and was walking without a limp. The range of knee motion was from 0° to 140°. There were no signs of infection.