Abstract
The objective of this work was the analysis of the genetic variability of Brucella melitensis in the departments of Libertador General San Martín, Ayacucho and Belgrano that belong to the province of San Luis, Argentina. For this purpose, flocks with different prevalence values of brucellosis were identified by conventional serological techniques as Buffered Plate Antigen Test (BPAT), Fluorescence Polarization Assay (FPA) and Complement Fixation Test (CFT). Samples of spleen, lymph nodes, liver, testis, epididymis, semen, milk, and synovial fluid and abomasal contents of abortions from a total of 104 animals were processed, of which 98 were goats and 6 were sheep. 32 isolates of B. melitensis biovar 1 were obtained and identified by classical bacteriological methods. Also, the presence of the pathogen in tissues samples was evidenced by PCR. An animal was considered positive for PCR for B. melitensis when a specific band was obtained in at least one of the tissues from the same animal. After the molecular detection of B. melitensis in tissues with isolation, DNA samples from tissues from which it was not possible to isolate were analyzed and it was possible to demonstrate the presence of the agent in 62 animals (including 4 sheep). As genotyping method, the MLVA 16 scheme was used, which uses the variability of 16 molecular markers to generate an unequivocal individualization of the genomes of B. melitensis from different animals. The genotypes were analyzed to determine the phylogenetic relationship between them and their georeferenced data were added to have complete information on the presence and circulation of different genotypes in each department. This study allowed identifying 21 circulating genotypes in the goats from the different departments. The phylogenetic relationship model found some of the genotypes described as potential candidate founders of the lineage that is distributed in different areas of the province. The discriminatory ability of the technique in a real epidemiological situation was confirmed, including discriminating genotypes within the same herd. The genotypes from this work were no previously described in any international data base.
