- Distinguished from other prokaryotes and placed in the class Mollicutes because they lack a true cell wall and consequent rigidity.
- This is a stable characteristic exhibited by the genera Mycoplasma, Ureaplasma and Acholeplasma and is distinct from cell wall-deficient and L-forms of other species.
- The outer membrane, the outermost layer, functions as the major antigenic interface.
- It is a flexible triple-layered structure of proteins and liquids.
- Many species also contain cholesterol in the membrane, which is absent from other bacterial cells.
- The important species is M. pneumoniae, but M. hominis and U. urealyticum may cause genital tract infection.
- Transmission of M. pneumoniae from person to person by airborne route.
- Other mycoplasmas and ureaplasmas can be transmitted by sexual contact.
- M. pneumoniae is an important cause of ‘atypical pneumonia’.
- Mycoplasma also associated with genital infection and with joint and other inflammatory infections.
- Other mycoplasmas are important pathogens of animals and birds.
- Many subspecies are fastidious, and complex media and soft agar may be required for satisfactory culture.
- Cultures incubated for at least seven days although some species grow readily on moist blood agar plates within 48 hours.
- Cells very variable in size (up to 100 µm) and morphology; cannot be stained by Gram’s stain, but impression of colonies can be stained with Romanowsky’s stains.
- Diagnosis of infection based on serology due to difficulties of culture.