ABSTRACT
This chapter presents the information on virulence factors that have been grouped according to their modes of action. The small amount of enterotoxin produced in transit may be insufficient to be harmful or may be inactivated by intestinal secretions. Infections are initiated on the surfaces of the mucous membranes or through breaks in the skin. Most infections actually begin on the mucous membranes of the respiratory, gastrointestinal or urogenital tracts. In these environments, the potential pathogen must first adhere to the host cell. Adherence is a complex process involving specific components not only of the microbial cell but also of the host cell to which the adhesins bind, in vitro work with cell and organ cultures has helped to identify some of the receptors. Pathogens must be able to withstand attack by PMNs and macrophages, the professional phagocytes, whose job it is to rid the body of invading organisms by ingestion and destruction.
