In the modern world, with a poor environmental situation, there is a certain ‘‘erasure” of the boundaries between pathogenic, opportunistic microorganisms and commensals, the number of antibiotic-resistant bacterial strains is growing. The microbiome of the human body is made up of more than 500 types of microorganisms, representing an integral ecological system, which is in a state of dynamic equilibriumwith macroorganism. Colonization of various biotopes is carried out by the formation of a biofilm, which represents several layers of microorganisms covered with a common glycocalyx and enclosed in a highly hydrated exopolysaccharide-mucin matrix. Under certain conditions, opportunistic bacteria can become causative agents of purulentinflammatory diseases, i.e. the mechanism of autoinfection is realized with a decrease in the body’s resistance or their translocation into unusual biotopes.