E. COLI STEC MONITORING IN A ONE HEALTH APPROACH.

This PhD thesis investigates the epidemiology of Shiga toxin-producing Escherichia coli (STEC) in dairy herds, employing a One Health approach to enhance surveillance and public health interventions. Recognizing the significant public health threat posed by STEC, particularly its association with severe gastrointestinal diseases and hemolytic uremic syndrome (HUS), this research aims to provide a comprehensive understanding of the pathogen's dynamics across human, animal, and environmental interfaces. The introduction outlines the historical context of E. coli discovery and its classification into various serogroups and serotypes, with a particular focus on the pathogenic STEC strains that have emerged as critical public health concerns since the first recognized outbreak in 1982. The study emphasizes the importance of understanding virulence factors, such as Shiga toxins and the locus of enterocyte effacement (LEE), which contribute to the pathogenicity of STEC. The role of animal reservoirs, particularly ruminants, is highlighted as they serve as asymptomatic carriers, facilitating zoonotic transmission to humans. The methodology section details the rigorous sampling and molecular diagnostic techniques employed, including Real-Time PCR assays for detecting STEC serogroups. The study encompasses sample collection from various matrices, DNA extraction protocols, and validation of molecular methods to ensure reliability in detecting STEC strains. In-silico analyses on whole genomes retrieved from literature provide insights into the virulence and transmission dynamics of these pathogens. Results indicate a significant prevalence of STEC in dairy herds, with varying serotype distributions across different environments. The findings underscore the necessity for enhanced monitoring systems that integrate molecular diagnostics to identify high-risk populations and inform targeted interventions. The discussion contextualizes these results within existing literature, exploring implications for public health policies aimed at reducing STEC transmission from livestock to humans. In conclusion, this thesis contributes valuable knowledge to the field of public health sciences by elucidating the complex interactions between STEC, its animal reservoirs, and human health risks. The integration of a One Health perspective not only enhances understanding of STEC epidemiology but also advocates for collaborative efforts among veterinary, agricultural, and public health sectors to mitigate the risks associated with this pathogen. Future research directions are proposed to further investigate non-O157 STEC strains and their emerging threats to food safety and public health. This work lays a foundation for developing more effective surveillance strategies and interventions that can ultimately reduce the burden of STEC infections globally.