Chlamydial and Rickettsial Infections
WALTER REED ARMY INST OF RESEARCH WASHINGTON DC
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There is no more challenging dilemma than that presented to mammalian hosts by infection with chlamydiae and rickettsiae. These pathogens have adopted specialised mechanisms to assure satisfaction of their metabolic deficiencies bacterial replication, and therefore survival, can occur only within cells. Once inside the host, the intracellular infectious cycle is repeated as bacteria pass from infected cell to neighbouring cell, metabolically inert, and frequently disguised in host-derived material. Tissue destruction and pathology eventually follow, and are usually evident well before the host is immunologically aware of the invader. The dilemma for the host lies in the mechanisms at its disposal for elimination of sequestered intracellular parasites once awareness occurs. These mechanisms are few and, as we will discuss throughout the chapter, less than optimally effective.