Ureaplasma parvum
Ureaplasma parvum is a species of "Ureaplasma", a genus of bacteria belonging to the family Mycoplasmataceae. "Ureaplasma parvum" was formerly known as "Ureaplasma urealyticum biovar" 1. "Ureaplasma parvum" has been identified as being a commensal in the uterus as part of the microbiome in healthy women of reproductive age. In addition, this pathogen may latently infect the chorionic villi tissues of pregnant women, thereby impacting pregnancy outcome. Classification. "Ureaplasma spp". are one of the smallest known clonal bacteria. They are closely related to mycoplasmas as they lack a peptidoglycan cell wall, metabolize cholesterol, and require urea for ATP  synthesis. The Ureaplasma genus has 14 serotypes that are classified based on the 16S rRNA gene, the urease gene, and the multiple-banded antigen (MBA) gene. "U. parvum" has four serotypes (-1, -3, -6, -14) that were differentiated by variations in the MBA gene, a Ureaplasma surface antigen protein. Although "U. parvum" is known to be a commensal microorganism within healthy humans, its ability to become pathogenic may be due to its ability to easily acquire new genes via horizontal gene transfer (HGT). Sequencing of "U. parvum" samples isolated from clinical patients reveals a much more diverse set of strains  (at least 19), suggesting that further methods of classifying "U. parvum" should be investigated. Clinical relevance. The clinical implications concerning the pathogenicity of "U. parvum" have yet to be determined because of its recent establishment as a separate species from "U. urealyticum". Due to the species heterogeneity in "Ureaplasma spp". not being noted in clinical studies prior to their distinction from each other, it is possible that "U. urealyticym" is disproportionately overrepresented compared to "U. parvum". As a consequence, interpreting data on "Ureaplasma parvum" can be difficult since there are currently few studies that differentiate between the "Ureaplasma spp". Therefore , there is little substantial evidence that "U. parvum" causes any of the diseases that have been associated with "U. urealyticym", specifically inflammatory vulvovaginitis, male infertility and non-gonococcal urethritis (NGU), female urethritis and urethral pain syndrome, pelvic inflammatory disease, cervicitis, ectopic pregnancy, and female infertility. It is important for future studies to accurately differentiate between "U. urealyticum" and "U. parvum", as this will aid in the etiological analysis of NGU and other diseases. "Ureaplasma spp". lack a cell wall and are therefore resistant to antimicrobials that specifically attack the cell wall. For this reason, "Ureaplasma spp." are particularly difficult to  diagnose and eradicate, and unnecessary treatment can further encourage antimicrobial resistance. As a result, extensive testing and treatment of the "Ureaplasma spp". is not always recommended. Commensalism. "Ureaplasma parvum" is commensal in both males and females, where it attaches itself to the mucosal lining of the urogenital tract. Damage to mucosal linings results in the relocation of "Ureaplasma spp". to other physiological areas of the body, which can lead to infection and disease. "U. parvum" has been investigated as an opportunistic pathogen, however current studies question its contribution to urogenital infections. For example, a study conducted by Rumyantseva et al  showed that in female patients with varying vaginal microflora, "U. parvum" was the most prevalent mycoplasma. In normal vaginal microflora, 43.5% of samples were "U. Parvum" positive. Bacterial vaginosis and aerobic vaginitis samples were 59.9% and 23.9% "U. Parvum" positive, respectively. This study supports the symbiotic considerations between vaginal microflora (primarily normal and bacterial vaginosis) and mycoplasma such as "U. parvum." Current studies: "Ureaplasma parvum" in males. "Ureaplasma parvum" (and "U. urealyticum") have been linked to nongonococcal urethritis (NGU), but the "Ureaplasma spp". have also been found in many healthy men, allowing for considerable skepticism that the two are correlated . Similarly, links to prostatitis and infertility are difficult to establish due to its presence in control groups. In andrology studies, the presence of "U. parvum" in semen has been found to be significant. Various "Ureaplasma spp." isolates have been detected in semen via polymerase chain reaction (PCR) and immunofluorescent antibody assay. In 36.6% of washed samples, "U. parvum" was present. Andrology studies surrounding "U. parvum" demonstrated that the bacteria can remain on the spermatozoa even after washing. Current studies: "Ureaplasma parvum" in females. Current research indicates that "U. parvum" infections can cause pregnancy complications. In pregnant women with an intra -amniotic infection, "U. parvum" is the most common bacterium found. "Ureaplasma" spp. generally causes a more severe inflammatory response than other microbial infections. These infections can lead to preterm birth, maternal and fetal inflammation, placental inflammation (chorioamnionitis), and neonatal mortality. One study found that amniotic inoculation with a clinically isolated "U. parvum" serovar 14 causes preterm birth in animal models, while serovar 3 causes a low rate of preterm birth but a higher rate of neonatal mortality. Studies are ongoing.