Mycoplasma are the smallest free-living organisms we know of. They are unique in that they don’t contain a cell wall, and do not respond to Gram staining. They are largely resistant to commonly prescribed antimicrobial agents.
Mycoplasmal organisms are often associated with mucosal surfaces, such is found in the lungs, mouth, nose, throat, urogenital tract. They don’t typically extend into the submucosa, except if the person is immunocompromised. In this case they may enter the bloodstream and enter different organs. While there are 17 species (at least) of Mycoplasma found in humans, only four are thought to be responsible for most clinically significant infections.
These four species are:
- Mycoplasma pneumoniae (a cause of pneumonia)
- Mycoplasma hominis
- Mycoplasma genitalium
- Ureaplasma species
Fastidious and slow-growing bacteria
Mycoplasmas that are slow-growing and are very specific in their growing circumstances, making them hard to grow in culture, are:
- Mycoplasma genitalium
- Mycoplasma fermentans
- Mycoplasma pirum
- Mycoplasma penetrans
Polymerase chain reaction (PCR) testing, which tests for DNA and RNA, is useful for studying these bacteria, since they are hard to grow due to being too fussy to be easily grown in a lab.
What we know about Mycoplasma infections
- M. hominis and Ureaplasma are frequently detected in lower urogenital tracts of healthy adults
- M. hominis and Ureaplasma can produce vaginal and urethral infections
- Some other Mycoplasmas have been found outside of the genitals (for example in synovial joint fluids of people with rheumatoid arthritis)
- Women with cervicitis and pelvic inflammatory disease may have M. genitalium
- Men with urethritis could have M. genitalium
- M. penetrans has been found in the urine of children and homosexual males with HIV
- Mycoplasma and Ureaplasma species may be transmitted by direct contact between people – genitals or mouths (or a combination of both), mother to child at birth or in utero, by transplant, or in the case of M. pneumoniae, by molecules in the air
- Mycoplasma species do not cause vaginitis directly, but may proliferate and contribute.
- M. hominis has been isolated from the endometrium and fallopian tubes of about 10 per cent of women with salpingitis
- Ureaplasma may cause involuntary infertility
- Ureaplasma may cause placental inflammation and invade the amniotic sac early, causing adverse pregnancy outcomes
- M. hominis was found in the blood of about 20 per cent of women with postpartum or postabortal fever, but not from afebrile women who had abortions, or from healthy pregnant women
- M genitalium causes male urethritis, cervicitis, and pelvic inflammatory disease which can be clinically confusing, looking identical to Neisseria gonorrhoeae (gonorrhoea)