Nontuberculous mycobacterial infections of the skin: A retrospective study of 25 cases.

Background: Absence of a pathognomonic clinical picture and variable histologic findings often delay diagnosis of nontuberculous mycobacteria (NTM)-induced cutaneous infections, and antimicrobial therapy varies.

Objective: We sought to investigate the clinical, microbiologic, and pathological findings of cutaneous NTM infections and response to different treatments.

Methods: Records of patients with NTM infections of the skin confirmed by positive cultures or histologic findings were reviewed. Clinical, microbiologic, and epidemiologic data were collected and skin biopsy specimens were reassessed.

Results: The series included 25 cases, one diagnosed by histology and 24 by positive culture: 16 cases with Mycobacterium marinum, 3 of atypical Mycobacterium without species identification, and one each with M chelonae, M xenopi, M abscessus, M gordonae, and M fortuitum. One of 16 patients with M marinum developed tenosynovitis. Mean interval between clinical presentation and diagnosis was 7.1 months (range: 1-27.3 months). All isolates analyzed for antimicrobial susceptibility pattern were sensitive to clarithromycin.

Limitations: Limitations include methods of case collection, retrospective study, and relatively small number of patients.

Conclusions: Diagnosis of NTM should be confirmed by histology and bacteriology studies of tissue cultures. Strong clinical suggestion of M marinum infection warrants initial empirical treatment to prevent progression to deep infection. The recommended treatment as indicated by the results of the in vitro susceptibility and clinical response is clarithromycin.