The leprosy agents Mycobacterium lepromatosis and Mycobacterium leprae in Mexico.

BACKGROUND: Mycobacterium leprae was the only known cause of leprosy until 2008, when a new species, named Mycobacterium lepromatosis, was found to cause diffuse lepromatous leprosy (DLL), a unique form of leprosy endemic in Mexico. METHODS: We sought to differentiate the leprosy agents among 120 Mexican patients with various clinical forms of leprosy and to compare their relative prevalences and disease features. Archived skin biopsy specimens from these patients were tested for both M. leprae and M. lepromatosis using polymerase chain reaction-based species-specific assays. RESULTS: Etiologic species were confirmed in 87 (72.5%) patients, of whom 55 were infected with M. lepromatosis, 18 with M. leprae, and 14 with both organisms. The endemic regions of each agent differed but overlapped. Patients with M. lepromatosis were younger and were distributed across more states; their clinical diagnoses included DLL (n = 13), lepromatous leprosy (LL) (n = 34), and eight other forms of leprosy. By contrast, the diagnoses of patients with M. leprae did not include DLL but did include LL (n = 15) and three other forms of leprosy. Thus, M. lepromatosis caused DLL specifically (P = 0.023). Patients with M. lepromatosis also showed more variable skin lesions; the extremities were the most common sites of biopsy in these patients. Finally, patients with dual infections manifested all clinical forms and accounted for 16.1% of all species-confirmed cases. CONCLUSIONS: Mycobacterium lepromatosis is another cause of leprosy and is probably more prevalent than M. leprae in Mexico. It mainly causes LL and also specifically DLL. Dual infections caused by both species may occur in endemic areas.

Identification of the leprosy agent Mycobacterium lepromatosis in Singapore.

BACKGROUND: A new leprosy-causing species, namely Mycobacterium lepromatosis, was discovered recently to be the cause of diffuse lepromatous leprosy (DLL) in Mexico. It is unknown whether this organism exists beyond Mexico. METHODS: We sought to determine the identity of the mycobacteria in the skin tissue of two patients from Singapore who died of DLL. DNA was extracted from archived biopsy tissue, and conserved polymerase chain reaction primers were used to amplify and sequence two to three mycobacterial genes in each skin sample. RESULTS: Both M. lepromatosis and the well-known leprosy agent Mycobacterium leprae were identified in each DLL skin sample. The M. lepromatosis gene sequences from the Singapore cases matched 99.9% with the known Mexican M. lepromatosis strain, but they only matched the corresponding M. leprae sequences by 89.2%. CONCLUSIONS: The new species M. lepromatosis exists beyond Mexico and is the cause of DLL in Singapore. It may cause dual infections along with M. leprae in endemic areas. Archived skin biopsy can be used to differentiate the leprosy agents.