Drug resistance pattern of Mycobacterium leprae from mouse footpad cultivation between 1997 to 2013 in Malaysia

Background: After three decades of implementing multidrug therapy (MDT) consisting of rifampicin, dapsone and clofazimine in Malaysia, the drug resistance pattern of Mycobacterium leprae is a growing concern as it may lead to failure of treatment and relapse of disease. Objective: To determine the drug resistance patterns of M. leprae in Malaysia. Methods: Mouse footpad (MFP) culture of all skin biopsy samples from patients with borderline lepromatous and lepromatous leprosy sent to the Leprosy Unit, National Public Health Laboratory, Sungai Buloh, Malaysia between 1997–2013 were retrospectively studied. Results: There were 651 MFP cultures performed. The mean age of patients was 41 years old (range: 6–88). The male:female ratio was 3·8:1. Four hundred and fortyfour patients (69·1%) were Malaysian. The rate of positive M. leprae culture was 66·6% (433 of 651). The mean Bacteriological Index (BI) and median Morphological Index (MI) for those with positive culture were 3·7 and 2·8 respectively. The mean BI and MI of those which failed to grow in the MFP were significantly lower than those with positive cultures (P , 0·001). Dapsone has the highest resistance rate of 55% (238 of 433). Nevertheless, high degree dapsone resistance (0·01%) was 6·24%. There were 407 MFP tests using rifampicin 0·003% and 12 (2·9%) were resistant to it. Clofazimine has the lowest intermediate degree (0·001%) resistance rate of 0·2% (1 of 429). There were no significant differences between the drug resistance pattern and the gender or the nationality of the patients. Conclusion: More than half of our positive MFP cultures showed low-level resistance to dapsone; less than 3% were resistant to rifampicin, and clofazimine resistance remained very low.