Mycoplasma pneumoniae is one of three species of Mycoplasma that frequently cause infection in humans. Mycoplasmas are ubiquitous and are the smallest organisms that can survive alone in nature. M. pneumoniae most commonly causes upper respiratory tract infections, but can also cause pneumonia. Many extrapulmonary manifestations have been described, although a causal link has not been established for many of these.
The clinical features, diagnosis, and treatment of infections, primarily pneumonia, caused by M. pneumoniae in adults will be reviewed here. M. pneumoniae infections in children as well as M. hominis infections are discussed separately. (See "Mycoplasma pneumoniae infection in children" and "Mycoplasma hominis and Ureaplasma urealyticum infections".)
The term "mycoplasma" is widely used to refer to any organism within the class Mollicutes that is composed of five genera (Mycoplasma, Ureaplasma, Acholeplasma, Anaeroplasma, and Asteroloplasma). Over 120 named Mycoplasma species exist and 13 Mycoplasma species, two Acholeplasma species, and one Ureaplasma species have been isolated from humans. However, only four species are well-established human pathogens :