Resumen de Genomic epidemiology: From transmission to the evolution of pathogenic microorganisms
Genomic epidemiology has revolutionized the microbial world. Its applications allow to know and better understand the behavior, transmission and evolution of microorganisms. Despite its great and recognized potential, its use is still limited, especially in developing regions.
The main objective of this thesis was to study and analyze the complete genomes of three pathogenic and zoonotic microorganisms to better understand their epidemiology, pathogenic potential and evolution.
In the first chapter, we characterized at the genomic level Salmonella enterica isolated from food, farms, and clinical samples in Ecuador. In addition, we presented evidence of the presence of virulence factors and a megaplasmid with genes encoding antimicrobial resistance and tolerance to environmental stress. Due to the phylogenetic relationship between isolates, we conclude the transmission of S. enterica through the consumption of chicken in Ecuador, and the urgent need for better control of the use of antimicrobials in poultry farms.
In the second chapter, genomic epidemiology was applied to isolates of Listeria monocytogenes, a microorganism that has received little attention in Ecuador despite its high rate of hospitalization and mortality worldwide. We compared the genomes of clinical and food isolates and inferred the epidemiological relationship through the food chain to humans in this country. We characterized isolates that, despite their susceptibility to antimicrobials, have significant pathogenic potential due to the presence of pathogenicity islands associated with severe disease. In addition, we established the need to implement routine surveillance of this pathogen and to search for other foods as possible sources of transmission of listeriosis in Ecuador.
The third chapter focused on the evaluation of genetic recombination among pathogenic species of Leptospira. The analysis was performed amid species, intra L. interrogans and among genes of the LPS locus, important for the diagnosis and development of vaccines for leptospirosis. With the results of this section, we suggest the existence of a selective pressure promoting genetic variation of this locus and of several genes, making of Leptospira a successful zoonotic pathogen.
