Book excerpt: The textbook was compiled in accordance with officially approved teaching programs for microbiology, virology and immunology in all faculties of higher medical schools. Questions of general microbiology (basic methods of studying microorganisms, morphology, structure and classification of bacteria, their physiology, the influence of physical, chemical and biological factors on microorganisms, microbial genetics and biotechnology, antimicrobials and the concept of infection) and special microbiology (morphology, physiology, pathogenic properties of pathogens of many infectious diseases, modern methods of their diagnostics, specific prevention and therapy). The textbook also contains sections on virology, protozoology, mycology and helminthology, which examine the basic biological properties of the causative agents and the diseases they cause. A significant part of the textbook is devoted to questions of immunology (nonspecific resistance of the organism, the doctrine of antigens, the immune system of the body, immune response, immunity reactions, allergy and other types of immune responses, immunodiagnostics and immunocorrection, immunoprophylaxis and immunotherapy). The textbook contains sections on clinical and sanitary microbiology, examines the ecology of microorganisms, the normal microbiota of the human body and the effect of microorganisms on the fetus. Separate sections are devoted to the microbiota of the oral cavity and microbiological research in stomatological and pharmaceutical fields. The textbook is intended for students of medical universities, relevant departments of higher education of doctors, interns and microbiologists of all specialties.