The clinical significance (or practical importance) of these bacteria in humans may be underestimated. While most of these Mollicutes do not cause any disease in humans, a few have been known to cause serious disease. (Please refer to Table 1.)
The microorganisms listed below can cause mild to serious infections, depending on different factors (which will be discussed on the Epidemiology page).
- Isolation of Mycoplasma pneumoniae from the respiratory tract must be correlated with clinical symptoms.
- Isolation of any of these organisms from normally sterile body sites is significantly associated with true disease.
- CDC does not recommend routine screening for Ureaplasma or M. genitalium.
Table 1. Clinical Significance of the Notable Cell Wall-Deficient Bacteria in Humans
| Notable Cell Wall-deficient Bacteria in Humans | Clinical Significance | Comments |
| Mycoplasma pneumoniae | Lung infection; community-acquired pneumonia; may also lead to infections of skin, central nervous system, blood, heart, and joints | Known as "atypical pneumoniae" |
| Mycoplasma genitalium | Sexually-transmitted infection (penis, cervix, rectum) | Significant cause of urethritis in men, female cervicitis, and pelvic inflammatory disease; not usually present as a commensal organism. |
| Mycoplasma hominis | Urogenital infections; complications of pregnancy; pelvic inflammatory disease, arthritis, osteoarthritis, wound infections, and several serious neonatal conditions (pneumonia, meningitis, bacteremia, abscesses) | Common as a commensal organism, especially in asymptomatic sexually active women. |
| Ureaplasma parvum | May lead to infertility; although not usually involved in true infections; may cause a variety of conditions in adults and neonates - may be isolated from tissues of spontaneously aborted fetuses/stillborns/premies - it is thought these organisms may infect the chorioamnion | Common as a commensal organism in lower urogenital tract |
| Ureaplasma urealyticum | Urologic, gynecologic, and obstetric significance; chorioamnion infection (stillbirth, pneumonia, meningitis, neonatal infection), pelvic inflammatory disease, nonspecific urethritis in males, infertility | Not found in vaginal microflora of healthy women/not a commensal organism |
7. CDC/Dull. Image #21527. "This image depicted an anteroposterior (AP) chest x-ray, revealing the pathologic changes of the lung fields in a case of a patient with mycoplasma pneumonia, caused by the bacterium, Mycoplasma pneumoniae. Note the infiltrate that had spread throughout the left middle and lower lobes, as well as the bilateral hilar involvement, indicating hilar adenopathy." PHIL public domain. Created 1966. Accessed December 29, 2023. https://phil.cdc.gov/Details.aspx?pid=21527
