Nakanaga Kazue, Saito Hajime, Ishii Norihisa, Goto Masamichi
Department of Bioregulation, Leprosy Research Center, National Institute of Infectious Diseases, 4-2-1, Aoba-cho, Higashimurayama-shi, Tokyo 189-0002, Japan.
Kekkaku. 2004 May;79(5):333-9.
Buruli ulcer is a human skin disease caused by Mycobacterium ulcerans infection, which is characterized by massive skin ulceration and persistent necrotic change. In recent years Buruli ulcer has rapidly emerged as an increasingly important cause of human morbidity around the world. The disease is endemic at least 32 countries in Africa, Western Pacific, Asia and South America, and it is considered the third most common mycobacterial infection of humans after tuberculosis and leprosy. An effective chemotherapeutic regimen against Buruli ulcer disease has not been established to date. In this study, the inhibitory effect of rifalazil (RLZ) against M. ulcerans was assessed in experimentally infected mice and compared to that of rifampicin (RFP).
Five-week-old BALB/c female mice were challenged with 25 microliters (CFU = 4 x 10(4) of M. ulcerans cultured in Middlebrook 7H9 broth in bilateral hind footpads. Mice were administered per os with a suspension of RLZ or RFP at 2.5, 5, or 10 mg/kg once daily 5 times per week starting from one day up to 6 weeks after infection. During the treatment, mice were observed weekly for footpad skin lesions and examined for footpad swelling. In addition, CFU enumeration was done on both hind footpads and spleen at 2, 4, and 6 weeks after initiating treatment.
In the infected control mice group, slightly erythematous lesions and moderate swelling of footpads were observed 4 weeks after the infection. Ulcerative lesion was observed 6 weeks after the infection. Mean log10 CFU/footpad (FP) was 5.22 on day 1 after the infection and increased to 5.56, 6.29, and 7.33 at 2, 4, and 6 weeks after treatment was initiated in the treated groups. On the other hand, no visible erythema, swelling or ulcerative lesion in footpads were observed in RLZ-administered groups. Furthermore, log10 CFU/FP decreased to 4.14 after only 2 weeks of initiating treatment in 2.5 mg/kg administered group, i.e. the lowest dose employed group. Log10 CFU/FP decreased to < 2.1 in 6 weeks in the 10 mg/kg administered group, which was close to the detection limit (< 1.7) of the CFU assay. By contrast, inhibitory effect on disease progression and reduction of CFU were observed only in the group of mice given 10 mg/kg among RFP-administered groups: the reduction of CFU was not observed in the early period but 6 weeks after initiating treatment.
These results clearly demonstrate that the in vivo anti-M.ulcerans activity of RLZ is much higher than RFP. RLZ activity against M. ulcerans can be expected to control the disease progression in the clinical applications.
布鲁里溃疡是由溃疡分枝杆菌感染引起的一种人类皮肤疾病，其特征为大面积皮肤溃疡和持续性坏死变化。近年来，布鲁里溃疡已迅速成为全球范围内人类发病的一个日益重要的原因。该疾病在非洲、西太平洋、亚洲和南美洲的至少32个国家呈地方性流行，被认为是继结核病和麻风病之后人类第三常见的分枝杆菌感染。迄今为止，尚未确立针对布鲁里溃疡病的有效化疗方案。在本研究中，在实验感染的小鼠中评估了利福拉齐（RLZ）对溃疡分枝杆菌的抑制作用，并与利福平（RFP）进行了比较。
将5周龄的BALB/c雌性小鼠双侧后足垫接种25微升（CFU = 4×10⁴）在Middlebrook 7H9肉汤中培养的溃疡分枝杆菌。从感染后1天开始，每周5次，连续6周，给小鼠经口灌胃2.5、5或10毫克/千克的RLZ或RFP悬浮液。在治疗期间，每周观察小鼠的足垫皮肤病变并检查足垫肿胀情况。此外，在开始治疗后2、4和6周对双侧后足垫和脾脏进行CFU计数。
在感染对照组小鼠中，感染后4周观察到足垫轻微红斑病变和中度肿胀。感染后6周观察到溃疡性病变。感染后第1天，平均log₁₀CFU/足垫（FP）为5.22，在治疗组开始治疗后2、4和6周分别增加到5.56、6.29和7.33。另一方面，在给予RLZ的组中，未观察到足垫有可见的红斑、肿胀或溃疡性病变。此外，在2.5毫克/千克给药组（即所用最低剂量组），仅在开始治疗2周后，log₁₀CFU/FP就降至4.14。在10毫克/千克给药组中，6周内log₁₀CFU/FP降至<2.1，接近CFU测定的检测限（<1.7）。相比之下，在给予RFP的组中，仅在给予10毫克/千克的小鼠组中观察到对疾病进展的抑制作用和CFU的减少：在早期未观察到CFU的减少，但在开始治疗6周后观察到。
这些结果清楚地表明，RLZ对溃疡分枝杆菌的体内活性远高于RFP。RLZ对溃疡分枝杆菌的活性有望在临床应用中控制疾病进展。
