As shown by RFLP analysis, there is a high variability in the beta-tubulin gene region of Leishmania sp. Such variability has been used in the identification of these parasites, establishing differences between subgenera of New World Leishmania. We have found a region of 500 bp (beta500) upstream of the coding region of the beta-tubulin gene that is present in all strains tested belonging to the L. (Viannia) subgenus. This region apparently is a repetitive sequence and we have shown that it is specific to the Leishmania (Viannia) subgenus. This sequence has no homology with the genomic DNA isolated from either the species belonging to the L. (Leishmania) subgenus or other Kinetoplastida, such as Trypanosoma cruzi, T. brucei, Leptomonas samueli, or Crithidia fasciciulata. The beta500 sequence showed sufficient variation to be used as a molecular marker in the identification of parasites. We established inter- and intrasubgenus differentiation and were able to discriminate at the species level in the Vianna subgenus. A PCR assay confirmed the specificity of the beta500 sequence.
The strategies implemented to identify pathogenic strains of Salmonella in countries with high production and consumption when is of chicken meat [such as Mexico), successfully bring germ-free meat to the market. Two Salmonella enterica enterica strains obtained from Mexican chicken meat were completely sequenced. The genomic comparison with the CT18 Salmonella strain indicates that strains 103 and 2199 vary by 1.9%. Genome analysis of the isolated strains revealed the presence of numerous virulence genes, as well as antibiotics resistance genes in these two isolates. Their potential pathogenicity was inferred from presence of 22 (103 strains) and 19 genes (2199 strains) homologous to the one annotated in Salmonella enterica virulome databanks. The characterization of these strains will contribute to successful Salmonella monitoring in Mexico.
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