Escherichia coli, is a ubiquitous bacterium with a significant role in the world of microbiology. It has garnered attention as a model organism, a vital component of the human microbiome, and a subject of concern due to its pathogenic strains. E. coli is the most prevalent commensal-type species of the family Enterobacteriaceae (Genus Escherichia), inhabiting the gastrointestinal tracts of warm-blooded animals and humans. The classification of E. coli based on pathogenicity is a critical distinction in understanding its impact on human and animal health. E. coli can be broadly categorized into two main groups: non-pathogenic and pathogenic strains, each with distinct characteristics and implications for host organisms. Non-pathogenic E. coli primarily reside in the gastrointestinal tract of humans and animals and are considered the major commensal organisms. The commensal has co-evolved with their hosts and play an essential role in maintaining the gut microbiome. They help digest complex carbohydrates and maintain a balanced microbial community (‘eubiosis’), which is crucial for digestion and overall physical and mental health. The non-pathogenic strains compete with potential pathogens for nutritional resources and host cellular receptors, helping to prevent the colonization and overgrowth of gut pathogens. Non-pathogenic E. coli strains are typically harmless and do not cause disease in the host. They remain confined to the lumen of the intestine, causing no significant harm to the host organism. Pathogenic E. coli strains, on the other hand, are associated with a range of diseases in both humans and animals. The strains have acquired various virulence factors, which enable them to colonize host tissues and cause infections. Some notable diseases caused by pathogenic E. coli include urinary tract infections (UTI) caused by uropathogenic E. coli (UPEC), gastroenteritis caused by enteropathogenic E. coli (EPEC), enterotoxigenic E. coli (ETEC) and haemolytic uremic syndrome (HUS). In animals, pathogenic E. coli strains are linked to various diseases, including diarrhoea in farm animals, oedema disease in pigs, dysentery in calves and lambs, and urinary tract infections in dogs and cats. Additionally, they can cause mastitis in bovines.