To identify the most active curative treatment of Buruli ulcer, two regimens incorporating the use of rifampin (RIF) were compared with the use of RIF alone in a mouse footpad model of Mycobacterium ulcerans infection. Treatments began after footpad swelling from infection and continued for 12 weeks with five doses weekly of one of the following regimens: (i) 10 mg of RIF/kg alone; (ii) 10 mg of RIF/kg and 100 mg of amikacin (AMK)/ kg; and (iii) 10 mg of RIF/kg, 100 mg of clarithromycin (CLR)/kg, and 50 mg of sparfloxacin (SPX)/kg. The activity of each regimen was assessed in terms of the reduction of the average lesion index and acid-fast bacillus (AFB) and CFU counts. All three regimens displayed various degrees of bactericidal activity against M. ulcerans. The ranking of bactericidal activity was found to be as follows: RIF-AMK > RIF-CLR-SPX > RIF. RIF-AMK was able to cure M. ulcerans-infected mice and prevent relapse 26 weeks after completion of treatment. To determine the impact of different rhythms of administration of RIF-AMK on the suppression of M.ulcerans growth, mice were given the RIF-AMK combination for 4 weeks but doses were administered either 5 days a week or twice or once weekly. After completion of treatment, the mice were kept under supervision for 30 additional weeks. M. ulcerans was considered to have grown in the footpad if swelling was visually observed and harvests contained more than 5 ؋ 10 5 AFB per footpad. The proportion of mice in which growth of M. ulcerans occurred, irrespective of drug dosage, was compared with the control mice to determine the proportion of M. ulcerans killed. Each dosage of RIF-AMK was bactericidal for M. ulcerans (P < 0.001), but the effect was significantly stronger in mice treated 5 days per week. The promising results of RIF-AMK treatment in M. ulcerans-infected mice support the clinical trial that is currently in progress under World Health Organization auspices in Ghana.Buruli ulcer or Mycobacterium ulcerans infection is the third most common mycobacterial disease after tuberculosis and leprosy. Large surgical excision of necrotic tissue, followed by skin grafting is, at present, the only treatment (21). The search for antimycobacterial drugs able to increase efficacy or substitute for surgical treatment is a priority.Using the kinetic method designed by C. C. Shepard for testing antileprosy drug activity in the mouse footpad (17), the following antimicrobials were assessed against M. ulcerans: clarithromycin (CLR), minocycline, sparfloxacin (SPX), rifampin (RIF), rifabutin, and amikacin (AMK). RIF, rifabutin, and AMK exhibited bactericidal activity, whereas CLR and SPX exhibited bacteriostatic activity; minocycline demonstrated no activity (3).Since the RIF-AMK combination was anticipated to be highly potent against M. ulcerans, we initially studied the curative efficacy of this combination. Treatment was given daily for 3 months after mouse footpad swelling from M. ulcerans infection had occurred. Because combined RIF-AMK requires the injection of AMK, a...

Mycobacterium ulcerans inoculated into the footpads of mice at 6 ؋ 10 3 CFU was shown to have a generation time of 6.5 days when estimated from weekly changes in microscopic counts of acid-fast bacilli (AFB) and 7.5 days when calculated from actual CFU enumerated on Lowenstein-Jensen egg medium incubated at 32°C. Footpads became swollen at week 10 (W10) after infection, and all infected control mice were dead at W15 after infection. Daily (5 days/week) treatment with 100 mg of clarithromycin (CLR)/kg of body weight beginning the day after infection prevented swelling of footpads at W10. When initiation of treatment was delayed until obvious footpad swelling was observed, there was a reduction in both the increase in AFB counts and deterioration of swollen footpads and also a prolonged survival of the mice to W18. Mice infected in the hind footpads with 5 ؋ 10 5 CFU of M. ulcerans were divided into an untreated control group and six treatment groups that received one of the following therapies for 8 weeks: 100 mg of CLR/kg, 25 mg of minocycline (MIN)/kg, 50 mg of sparfloxacin (SPX)/kg, 10 mg of rifampin (RIF)/kg, 10 mg of rifabutin (RBT)/kg, or 100 mg of amikacin (AMK)/kg. After completion of therapy, treated animals were observed for an additional 17 weeks. All control mice and mice treated with CLR, MIN, or SPX exhibited swollen footpads during the observation period. In contrast, of those animals treated with RIF, RBT, or AMK, none had footpad swelling and all inoculated cultures done after the W17 observation remained negative. These results suggest that RIF, RBT, and AMK may be effective in the treatment of human infection with M. ulcerans.Since its first description in Australia in 1948 by MacCallum and others (10), the Bairnsdale ulcer, subsequently named the Buruli ulcer, is currently reported with increasing prevalence in West and Central Africa. As described by van der Werf et al. (18), it is the third most common mycobacterial disease in humans after tuberculosis and leprosy. The usual clinical feature is a deep, necrotic, and painless ulcer with typically undermined edges resulting from coalescent necrosis of the subcutaneous fat with vascular occlusion. Large surgical excision of the necrotic tissue followed by skin grafting is, at present, the only treatment (18). The responsible organism is a slowly growing acid-fast and alcohol-fast mycobacterial species, Mycobacterium ulcerans. It grows at an optimal temperature of 32°C and is known to be resistant to most antituberculosis and antileprosy drugs (18).Experimental growth of M. ulcerans in immunocompetent mice has been studied extensively by Fenner (3). After intravenous, intraperitoneal, or intranasal infection with 10 4 to 10 6 CFU of M. ulcerans, disseminated skin lesions developed within the ensuing 10 to 24 weeks. In contrast, when the organisms were injected into the hind footpads, the lesions remained localized in the footpads, which subsequently became inflamed, swollen, and finally ulcerated after 3 to 6 weeks, depending upon the size of th...

Mice infected in the left hind footpad with 5 log 10 acid-fast bacilli of Mycobacterium ulcerans were divided into an untreated control group and 17 treatment groups that received one of the following regimens for 4 weeks (all doses in milligrams per kilogram): 100 mg of azithromycin (AZM), 100 mg of clarithromycin (CLR), or 50 mg of AZM for a duration of 5 days a week (daily), three times a week, or once weekly. In addition, the following regimens were administered daily: 100 mg of telithromycin (TLM), sparfloxacin (SPX), or moxifloxacin (MOX); 200 mg of levofloxacin (LVX); 100 mg of streptomycin (STR) or amikacin (AMK); 10 mg of rifampin (RIF); and the combination of 10 mg of RIF and 100 mg of AMK (RIF؉AMK). After completion of treatment, mice were observed for 30 weeks. The effectiveness of treatment regimens was assessed in terms of the delay in median time to footpad swelling in treated mice compared with that in the untreated controls. Clear-cut bactericidal activity, i.e., an observed delay in footpad swelling that exceeded the period of treatment, was observed in the STR-, AMK-, and RIF؉AMK-treated mice. However, all mice treated with either AMK or STR alone had swollen footpads before the end of the 30-week observation period, suggesting regrowth of M. ulcerans. In contrast, 50% of the mice treated with the RIF؉AMK combination exhibited no lesion even after 30 weeks, suggesting cure. The remaining regimens could be assigned to one of three groups: (i) no activity (50 mg of AZM, 100 mg of AZM thrice weekly, TLM, and LVX); (ii) bacteriostatic activity, i.e., a delay in footpad swelling shorter than the 4-week treatment duration (100 mg of AZM daily or once weekly, CLR thrice or once weekly, and MOX); or (iii) weak bactericidal activity (CLR daily and SPX). The RIF؉AMK combination and possibly RIF؉STR warrant further study for the treatment of M. ulcerans infection in humans.Mycobacterium ulcerans, the only toxin-producing mycobacterial species (5) is responsible for Buruli ulcer (BU), the third most prevalent mycobacterial disease throughout the world (20). Over the past 10 years, an increasing incidence of BU has been reported in several West African countries (6, 8) and Australia (4) and is now reported in most of sub-Saharan Africa, Central and South America, India, Southeast Asia, and Papua New Guinea (20).In vitro, M. ulcerans is susceptible to several antimicrobials, including rifampin (RIF), clarithromycin (CLR), streptomycin (STR), amikacin (AMK), sparfloxacin (SPX), and clofazimine (1,11,13,14,19). However, the clinical response of humans with BU to various antimicrobial regimens containing these drugs have not confirmed in vitro studies so that, to date, BU treatment still relies on extensive surgical excision of the lesions followed by skin grafting (20).In a previous study, the mouse footpad model of Fenner (3) was used to assess the in vivo activity of several drugs against M. ulcerans (2). CLR, for which in vitro activity against M. ulcerans has been demonstrated (11), exhibited only bacteri...

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