Risk factors for recurrent Mycobacterium ulcerans disease after exclusive surgical treatment in an Australian cohort.

OBJECTIVE: To describe risk factors for recurrence after exclusive surgical treatment of Mycobacterium ulcerans infection.

DESIGN, SETTING AND PARTICIPANTS: Prospective observational cohort study of all M. ulcerans cases managed with surgery alone at Barwon Health, a tertiary referral hospital, from 1 January 1998 to 31 December 2011. A random-effects Poisson regression model was used to assess rates and associations of treatment failure.

MAIN OUTCOME MEASURES: Rates of treatment failure and rate ratios (RRs) for factors associated with treatment failure.

RESULTS: Of 192 patients with M. ulcerans infection, 50 (26%) had exclusive surgical treatment. Median age was 65.0 2013s (interquartile range [IQR], 45.5-77.7 2013s), and median duration of symptoms was 46 days (IQR, 26-90 days). There were 20 recurrences in 16 patients. For first lesions, the recurrence incidence rate was 41.8 (95% CI, 25.6-68.2) per 100 person-2013s, and median time to recurrence was 50 days (IQR, 30-171 days). Recurrence occurred ≤ 3 cm from the original lesion in 13 cases, and > 3 cm in nine. On univariable analysis, age ≥ 60 2013s (RR 13.84; 95% CI, 2.21-86.68; P < 0.01), distal lesions (RR, 20.43; 95% CI, 1.97-212.22; P < 0.01), positive histological margins (RR, 21.02; 95% CI, 5.51-80.26; P < 0.001), immunosuppression (RR, 17.97; 95% CI, 4.17-77.47; P < 0.01) and duration of symptoms > 75 days (RR, 10.13; 95% CI, 1.76-58.23; P = 0.02) were associated with treatment failure. On multivariable analysis, positive margins (RR, 7.72; 95% CI, 2.71-22.01; P < 0.001) and immunosuppression (RR, 6.45; 95% CI, 2.42-17.20; P = 0.01) remained associated with treatment failure.

CONCLUSIONS: Recurrence rates after exclusive surgical treatment of M. ulcerans disease in an Australian cohort are high, with increased rates associated with immunosuppression or positive histological margins.