Infectious diarrhoea in dogs and cats is one of the most common maladies facing the small animal veterinarians. Veterinarians should be familiar with the basics of ethiology, epizoothiology, simptomatology, diagnostics, treatment and control of primary entheropathogenic bacteria in cats and dogs, including Clostridium difficile, Clostridium perfringens, Campylobacter spp., Salmonella spp., and Escherichia coli. Clinically, this manifest in non specific simptoms of a gastroenteritis and infections can also be subclinic, in which cases the animals excrete the bacteria via feces. Entheropathogenic bacteria can cause diarrhoea primarly or they can cause it together with some other microorganisms and or parasites. In most cases where bacteria are the source of the problem, it is not recommended to administer antimicrobial treatment, but is rather recommended to focus on supportive and simpthomatic therapy. The exception is animals with changed general condition. Due to zoonotic potential of all bacteria which can cause enteritis , it is important to isolate sick animals and also take other profilactic precautions to prevent spreading the infection on other animals and people.