RESUMEN
Current tendencies and problems of molecular biology and its application in infectious diseases are discussed. Basic stages of the development of molecular epidemiology as a leading tool for epidemiological studies are reviewed. More than 30 years ago, molecular epidemiology was first used to study nosocomial infections. Special attention is given to the achievements of Russian scientists, especially in the discovery of Astrakhan spotted fever Rickettsia, noncultured forms of Vibrio cholerae, and the microorganism "Montezuma." Also, the development of PCR-based methods of identification and typing of Mycobacterium tuberculosis by Russian specialists and its significant role in strategies for diagnosing and treatment of tuberculosis are discussed. Now, the most important field of application of molecular biology methods is bacterial evolution, especially with regard to pathogenic microorganisms and emerging infections. Searching for the novel pathogenic agents, establishment of the infectious nature of diseases with unclear origin, and determining the precise mechanisms of pathogenicity are most intriguing issues. So, molecular biology should play a major role both in clinical and research fields.