Presence, Pathogenicity, Antibiotic Resistance, and Virulence Factors of Escherichia coli: A Review

Escherichia coli (E. coli) is a Gram-negative, commensal/pathogenic bacteria found in human intestines and the natural environment. Pathogenic E. coli is known as extra-intestinal pathogenic E. coli (ExPEC) or intestinal pathogenic E. coli (InPEC). InPEC E. coli strains are separated into six pathogenic groups, known as enteropathogenic (EPEC), enterotoxigenic (ETEC), enteroinvasive (EIEC), enteroaggregative (EAEC), enterohaemorrhagic (EHEC), and diffusely adherent (DAEC), that have various virulence factors that cause infection. Virulence factors refer to a combination of distinctive accessory traits that affect a broad range of cellular processes in pathogens. There are two important virulence factors that directly interact with cells to cause diarrhoeal diseases within the intestines: adhesion and colonization factors and exotoxins. Virulence factors are crucial for bacteria to overcome the host’s immune system and result in antibiotic resistance. Antibiotics are used to combat the symptoms and duration of infection by pathogenic E. coli. However, the misuse and overuse of antibiotics have led to the global concern of antibiotic resistance. Currently, the antibiotic colistin is the last-resort drug to fight infection caused by this bacterium. Antibiotic resistance can be achieved in two main ways: horizontal gene transfer and mutation in different genes. The genetic basis for developing antibiotic resistance in E. coli occurs through four mechanisms: limiting drug uptake, modification of the drug target, inactivation of the drug, and active efflux of the drug. These mechanisms use different processes to remove the antibiotic from the bacterial cell or prevent the antibiotic from entering the bacterial cell or binding to targets. This prevents drugs from working effectively, and bacteria can acquire antibiotic resistance. E. coli is classified into different phylogenetic groups (A, B1, B2, D1, D2, E, and clade I). It is a very versatile bacterium that can easily adapt to different environmental factors. The present review gathered information about the pathogenicity, antimicrobial resistance, and phylogenetics of E. coli. These aspects are interconnected; thus, it will provide information on tracking the spread of pathogenic strains and antibiotic resistance genes of different strains using phylogenetics and how antibiotic resistance genes evolve. Understanding genetic variation in E. coli will help in monitoring and controlling outbreaks and in developing novel antibiotics and treatment. The increasing rate of antibiotic resistance, and the ability of E. coli to evolve rapidly, suggest that in-depth research is needed in these areas.