Mycoplasma and Ureaplasma
Mycoplasma belongs to class Mollicutes (Mollis, soft; cutis, skin),order Mycoplasmatales. This order contains four families— Mycoplasmataceae, Acholeplasmataceae, Spiroplasmataceae, and Anaplasmataceae; of which, most mycoplasma causing human infections belong to the family Mycoplasmataceae.
Family Acholeplasmataceae includes mostly saprophytic mycoplasmas; these mycoplasmas do not require sterols as growth factor. Family Spiroplasmataceae includes mostly mycoplasmas, which are parasites of arthropods and plants; they require sterols as their growth factor. Family Anaplasmataceae contains mycoplasmas that are strict anaerobes and are found in the intestinal tract of cattle and sheep.
The family Mycoplasmataceae includes parasite mycoplasmas, which require cholesterol or other sterols as growth factors. It consists of two genera—Mycoplasma and Ureaplasma. At least 13 species of genera Mycoplasma and Ureaplasma are known to colonize or cause diseases in humans.
· The genus Mycoplasma contains the pathogens that use glu-cose or arginine, but do not utilize urea. The genus contains over 90 species. These species occur as commensals, para-sites, and pathogens of a variety of plant insects and mam-malian hosts.
Mycoplasma pneumoniae is the most important speciesknown to cause infection in humans. Mycoplasma hominis,Mycoplasma fermentans, Mycoplasma pirum, Mycoplasma sali-varium, Mycoplasma orale, and Mycoplasma genitalium are theother pathogens that are commonly associated with human infections.
· The genus Ureaplasma includes the organisms that utilize urea. Genus Ureaplasma consists of 5 species of which Urea-plasma urealyticum is the most important species isolatedfrom infections of genital and respiratory tract in humans (Table 45-1).
Mycoplasmas are prokaryotes, but they differ from prokaryotes by having a unique cell membrane that contains sterols. Also, the mycoplasmas do not have a cell wall. Mycoplasmapathogens when first discovered were thought to be viruses or L form of bacteria.