Various genotypes of Mycobacterium leprae from Mexico reveal distinct geographic distribution.

OBJECTIVE: To classify Mycobacterium leprae isolates from multiple areas in Mexico based on variable number of tandem repeats of 6 base within the rpoT gene and three single nucleotide polymorphism (SNP), and to analyse their geographic distribution in the context of the origin of leprosy in Mexico. RESULTS: Analysis for rpoT genotyping of 64 samples collected in the west and southwestern areas revealed that 46 isolates were of the 4 copy type and 18 isolates were of the 3 copy type. All samples from the eastern coastal area (n = 24) and from the Yucatan peninsula (n = 12) were of the 3 copy type. Six isolates from the west and southwestern area were SNP-type 1, 13 isolates were SNP-type 2 and 45 isolates were SNP-type 3. Nineteen of 24 isolates from the eastern coastal area were SNP-type 3 and one was SNP-type 4. Seven isolates from the Yucatan peninsula were SNP-type 3 and one was SNP-type 4. CONCLUSION: The difference of the proportion of each genotype between the western areas and the eastern areas indicated the expansion of leprosy through different paths in Mexico.

A mycobacterial extracytoplasmic function sigma factor involved in survival following stress.

The extracytoplasmic function (ECF) sigma factors constitute a diverse group of alternative sigma factors that have been demonstrated to regulate gene expression in response to environmental conditions in several bacterial species. Genes encoding an ECF sigma factor of Mycobacterium tuberculosis, Mycobacterium avium, and Mycobacterium smegmatis, designated sigE, were cloned and analyzed. Southern blot analysis demonstrated the presence of a single copy of this gene in these species and in Mycobacterium bovis BCG, Mycobacterium leprae, and Mycobacterium fortuitum. Sequence analysis showed the sigE gene to be highly conserved among M. tuberculosis, M. avium, M. smegmatis, and M. leprae. Recombinant M. tuberculosis SigE, when combined with core RNA polymerase from M. smegmatis, reconstituted specific RNA polymerase activity on sigE in vitro, demonstrating that this gene encodes a functional sigma factor. Two in vivo transcription start sites for sigE were also identified in M. smegmatis and M. bovis BCG. Comparison of wild-type M. smegmatis with a sigE mutant strain demonstrated decreased survival of the mutant under conditions of high-temperature heat shock, acidic pH, exposure to detergent, and oxidative stress. An inducible protective response to oxidative stress present in the wild type was absent in the mutant. The mycobacterial SigE protein, although nonessential for viability in vitro, appears to play a role in the ability of these organisms to withstand a variety of stresses.