Efficacy of Rifampin Plus Clofazimine in a Murine Model of Mycobacterium ulcerans Disease

Paul J Converse,Si-Yang Li,John Adamson,Eric L Nuermberger,Yoshito Kishi,Sandeep Tyagi,Yalan Xing,Jacques H Grosset,Richard O Phillips

doi:10.1371/journal.pntd.0003823

Paul J Converse, Si-Yang Li + Show 7 more

Open Access

https://doi.org/10.1371/journal.pntd.0003823

Copy DOI

Abstract

Treatment of Buruli ulcer, or Mycobacterium ulcerans disease, has shifted from surgical excision and skin grafting to antibiotic therapy usually with 8 weeks of daily rifampin (RIF) and streptomycin (STR). Although the results have been highly favorable, administration of STR requires intramuscular injection and carries the risk of side effects, such as hearing loss. Therefore, an all-oral, potentially less toxic, treatment regimen has been sought and encouraged by the World Health Organization. A combination of RIF plus clarithromycin (CLR) has been successful in patients first administered RIF+STR for 2 or 4 weeks. Based on evidence of efficacy of clofazimine (CFZ) in humans and mice with tuberculosis, we hypothesized that the combination of RIF+CFZ would be effective against M. ulcerans in the mouse footpad model of M. ulcerans disease because CFZ has similar MIC against M. tuberculosis and M. ulcerans. For comparison, mice were also treated with the gold standard of RIF+STR, the proposed RIF+CLR alternative regimen, or CFZ alone. Treatment was initiated after development of footpad swelling, when the bacterial burden was 4.64±0.14log10 CFU. At week 2 of treatment, the CFU counts had increased in untreated mice, remained essentially unchanged in mice treated with CFZ alone, decreased modestly with either RIF+CLR or RIF+CFZ, and decreased substantially with RIF+STR. At week 4, on the basis of footpad CFU counts, the combination regimens were ranked as follows: RIF+STR>RIF+CLR>RIF+CFZ. At weeks 6 and 8, none of the mice treated with these regimens had detectable CFU. Footpad swelling declined comparably with all of the combination regimens, as did the levels of detectable mycolactone A/B. In mice treated for only 6 weeks and followed up for 24 weeks, there were no relapses in RIF+STR treated mice, one (5%) relapse in RIF+CFZ-treated mice, but >50% in RIF+CLR treated mice. On the basis of these results, RIF+CFZ has potential as a continuation phase regimen for treatment of M. ulcerans disease.

Highlights

Emerging evidence of the efficacy of the anti-leprosy drug clofazimine (CFZ) against tuberculosis prompted an evaluation of CFZ + RIF as well as another all-oral regimen, RIF + clarithromycin (CLR) in a mouse model of Buruli ulcer (BU)
The results showed that RIF+CFZ initially acts more slowly against M. ulcerans than RIF+STR or RIF+CLR but it stops mycolactone production and is as good as RIF+STR and better than RIF+CLR at preventing relapse of infection
Buruli ulcer (BU), or Mycobacterium ulcerans disease, has become a more readily treatable disease since 2004 with the transition from only surgery and skin grafting to antibiotic therapy with the combination of rifampin (RIF) and streptomycin (STR), the WHO preferred regimen or with RIF plus a fluoroquinolone or clarithromycin if STR is contraindicated, complemented by surgery in the case of extensive lesions to prevent or correct functional disabilities [1]

Summary

Introduction

Buruli ulcer (BU), or Mycobacterium ulcerans disease, has become a more readily treatable disease since 2004 with the transition from only surgery and skin grafting to antibiotic therapy with the combination of rifampin (RIF) and streptomycin (STR), the WHO preferred regimen or with RIF plus a fluoroquinolone or clarithromycin if STR is contraindicated, complemented by surgery in the case of extensive lesions to prevent or correct functional disabilities [1]. Initial trials with the RIF+STR regimen included few reports of ototoxicity, objective measurements of hearing loss indicate that it may occur rather frequently [2]. For this reason and operational issues with STR, an all-oral regimen is sought. There is hope that RIF plus clarithromycin (CLR) can be an acceptable oral regimen This regimen would still require eight weeks of drug administration and may be complicated by gastrointestinal intolerance and the induction of CLR metabolism by RIF [3,4,5,6,7]. RIF+CLR was inferior to RIF +STR and inferior to the combination of the long-acting rifamycin, rifapentine plus CLR whether assessed by bactericidal activity, regression of footpad swelling, or recurrence (relapse) of swelling after treatment completion [12]

Methods

Results

Discussion

Conclusion