The conse nt of the department is required. The objective of this course is to present concepts in pathogenesis by detailed study of the best available examples, not to provide a comprehensive study of all known pathogens. Initially we were to exclude bacteria but this field has expanded rapid ly and, as a consequence, MMI 405 now can be concerned with only some bacteria. The topics chosen to illustrate different themes in the strategies are employed by pathogen and host, as well as to draw on the expertise available within the faculty. Over the course of evolution, their animal hosts have developed mechanisms to hinder most of these pro cesses including, in particular, a complex immune response.
Different pathogens can solve the same problems in different ways.
For instance, skin is an effective mechanical barrier against infection. A number of vector-borne pathogens exploit the fact that biting insects breach this barrier. By necessity, s ince animals must take in oxygen and food and excrete wastes, there are points of more direct contact with the environment. Other pathogens can exploit this and avoid the barrier of the skin by specialized entry through the respiratory or digestive tract s, the conjunctiva, or the sex organs. The closer we look at pathogenic mechanisms, and the deeper our understanding becomes, down even at the molecular level, the more we see that the same pathogenic strategy can be achieved in different ways.