Walsh & Hoyt: Pathogenicity

Mycoplasmas are ubiquitous organisms that can be found in a variety of mammals, fish, insects, and plants. In animals, they primarily inhabit mucous surfaces of the respiratory and urogenital tracts. Because of the limited ability to synthesize many of their own cell structures, most mycoplasmas are parasites with specific organ and tissue targets. The determination of virulence of these pathogens is not completely understood. Colonization and infection occur from cytadherence through special adhesion proteins. Once adherent to the hosts cell surface, release of free radicals and injection of hydrolytic enzymes into the cell occurs. In some cases, the best studied of which is M. penetrans, the organism enters the host cell to reside in the cells immune-privileged cytoplasmic environment, thus allowing the pathogen to disrupt normal cell metabolism, cytoskeleton arrangement, and signal transduction. Some mycoplasmas have the potential for molecular mimicry inducing the production of autoantibodies and autoimmune disorders. Furthermore, phenotypic plasticity allows some mycoplasmas to avoid the constant surveillance and destruction of the hosts defense mechanisms. Mycoplasmas may have immunomodulating properties by influencing T and B-cell activation and affecting monocyte and macrophage function.