Throughout scientific literature, we can find evidence that antimicrobial resistance has become a big problem in the recent years on a global scale. Public healthcare systems all over the world are faced with a great challenge in this respect. Obviously, there are many bacteria that can cause infections in humans and animals alike, but somehow it seems that the greatest threat nowadays comes from the Enterobacteriaceae members, especially Escherichia coli. Namely, we are witnesses to the fact that the systems that these bacteria developed to fight off antibiotics are the strongest and most diverse in Enterobacteriaceae. Our great advantage is in understanding the systems that bacteria developed to fight off antibiotics, so these can help us understand the connection between these microorganisms and the occurrence of antibiotic-resistance both in humans and their pets. Furthermore, unfavorable conditions related to the ease of E. coli transmission via the fecal–oral route among humans, environmental sources, and animals only add to the problem. For all the above stated reasons, it is evident that the epidemiology of E. coli strains and resistance mechanisms they have developed over time are extremely significant topics and all scientific findings in this area will be of vital importance in the fight against infections caused by these bacteria.