FROM POPULATION-GENETICS OF BACTERIA TO EPIDEMIOLOGY OF INFECTIOUS-DISEASES

The bacterial world has been too often reduced to Escherichia coli. In fact, there is a tremendous bacterial diversity. Knowledge of the structure of bacterial populations is a prerequisite to the understanding of epidemiology of infectious diseases. The major bacterial groups defined by a phylogenetic approach based on ribosomal RNA studies clearly have a vertical evolution. Bacterial species, defined as biologic or phenetic entities, really exist. Within a species, bacteria occupy a spectrum of population structures ranging from highly sexual to almost strictly clonal according to the level of horizontal exchange.