Mycoplasmataceae

Several pathogenic and nonpathogenic Mycoplasma spp. have been identified in swine, and four species are responsible for nearly all diseases. Mycoplasma hyopneumoniae causes enzootic pneumonia and is an important primary pathogen in swine. Mycoplasma hyorhinis most commonly causes polyserositis and arthritis in nursery-age pigs. Mycoplasma hyosynoviae causes arthritis in growerfinisher pigs, and Mycoplasma suis, formerly Eperythrozoon suis, causes infectious anemia in pigs. Mycoplasmas are the smallest and simplest known self-replicating organisms, phylogenetically related to gram-positive bacteria. They are distinguished from other eubacteria by lacking a cell wall, having cholesterol in the plasma membrane, a low genomic G+C content, and unique usage of the UGA codon for tryptophan. Most Mycoplasma spp. attach to and replicate on epithelial cells that line the respiratory and urogenital tracts, as well as the conjunctiva, digestive tract, mammary glands, and joints. In contrast, M. suis attaches to, invades, and replicates on and in red blood cells.