Book Description

Escherichia coli are one of the microorganisms most frequently studied worldwide. They are Gram-negative bacilli, facultative anaerobic, rod-shaped bacterium, which are most often found in the gastrointestinal tract as a normal coloniser of warm blood organisms (mainly in mammals, but are also present in birds, reptiles and fish). Taxonomically, E. coli belong to the Enterobacteriaceae family and are an important component of the intestinal microbiota, being involved in some essential metabolic processes such as the production of vitamin K and vitamin B12. E. coli also help to maintain the anaerobic environment needed for most of the microbiota by consuming oxygen that enters the gut and competitively exclude pathogens from the lower intestine of their hosts. E. coli can also adapt to life in an external environment outside hosts, such as soil, water, plants and food, due to their hardiness and metabolic flexibility. Despite establishing symbiotic relationships, this well-known microorganism can also have an important pathogenic role within their hosts, especially from a human point of view. It is able to cause a wide variety of infections that can reach a high prevalence and even cause significant morbidity and mortality. According to a recent report on this topic, it is predicted that three million people will die from a drug-resistant E. coli infection by 2050 if no measures are taken to tackle the problem of antimicrobial resistance. Although this figure exceeds that expected in a developed continent, it demonstrates the presence of an emerging health threat - antimicrobial resistance. Bacterial pathogenicity is defined as the genetic capacity of the bacterium to cause disease, based on the virulence and resistance traits it possesses. Unfortunately, E. coli can easily acquire this capacity and is considered a major cause of human infectious disease worldwide. In order to better understand the double component of the pathogenicity of E. coli, it is important to accurately define two concepts: virulence and resistance. Virulence is the pathogenic ability to cause damage in a host and is mediated by the expression of combined virulence factors. Resistance is the capacity to persist and grow in a determinate environment taking into account different variables such as temperature, pH conditions or antimicrobial concentrations. The antimicrobial resistance of E. coli is a worrisome aspect, which is very important and difficult to manage. This PhD dissertation is focused on the study of the molecular bases of the most prevalent antimicrobial resistance mechanisms in E. coli as well as the prevalence of different VFGs in various intestinal and extraintestinal E. coli infections in order to better understand the pathogenic aspects of this bacterium in human hosts.