Surgical Site Infections Caused by Rapidly Growing Nontuberculous Mycobacteria: an Under-Recognized and Misdiagnosed Entity

Rapidly growing nontuberculous mycobacteria (NTM) such as M. fortuitum and M. chelonae are ubiquitous; have been isolated from natural water, tap water, and water used in showers in hospitals; and can cause surgical site infections. A retrospective chart review at a tertiary care referral hospital was carried out. Patients with SSI in whom wound cultures grew rapidly growing NTM or histopathological examination (HPE) showed granulomatous inflammation were included. A total of 50 patients were analyzed. Thirty-one patients had had laparoscopic surgery, and nineteen had had open surgery. Average time of presentation after surgery was 40 days (range 7 to 90 days). Clinical features included delayed wound healing, chronic discharge at the surgical site, nodular swelling, and sinus tract formation. Histopathology showed granulomatous inflammation in 40 patients with acid-fast bacilli stain positive in 2 patients. Mycobacterial culture was positive in 16 patients: 12 grew M. fortuitum , 2 grew M. abscessus , and 2 had rapid growers that could not be speciated further. Six of these sixteen culture-positive cases also had histopathology showing granulomatous inflammation. All isolates were sensitive to clarithromycin, amikacin, levofloxacin, imipenem, and tigecycline. Forty-two patients received surgical debridement in addition to medical management. Eight patients were treated with medical management alone since they had small nodular lesions or minimal discharge. Medical therapy was with clarithromycin and either levofloxacin or moxifloxacin for 4–6 months, with amikacin for the first 2 months. Of the 50 patients, forty-two recovered completely, 7 were on follow-up and doing well clinically, and one patient was lost to follow-up. Rapidly growing NTM infection should be suspected in patients with delayed onset SSI or chronic discharging sinuses, especially after laparoscopic surgery. The diagnosis can be confirmed by mycobacterial culture and HPE. Response is usually good with surgical debridement, followed by a combination of clarithromycin, quinolones, and amikacin for 4–6 months.