Ureaplasma urealyticum pathophysiology
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Ureaplasma species have been associated with several conditions such as preterm delivery, perinatal mortality, neonatal infection, and urogenital infection in adults. Stimulation of host inflammatory responses by Ureaplasma has been implicated in most of these conditions.
The role of Ureaplasma infection in preterm delivery
- Ureaplasma species are considered to be of low virulence, and 40-80% of healthy women have Ureaplasma species (U. urealyticum and U. parvum) in their genital tract.
- Controversial evidence exists supporting the association between genital colonization by Ureaplasma species and complications of pregnancy such as preterm delivery.
- Lactobacilli help maintain the vaginal acidity, preventing the invasion of bacteria. However, the urease activity of Ureaplasma species such as U. urealyticum increases the pH of the vagina via the hydrolysis of urea into carbon dioxide and ammonia. This increases the susceptibility to mixed infection with other pathogenic bacteria.
- Ureaplasma and other pathogenic bacteria induce the secretion of pro-inflammatory cytokines such as IL-1, TNF-α, IL-6, and chemokines such as IL-8, leading to the recruitment of leukocytes and production of prostaglandins. Uterine stimulation by prostaglandins result in preterm delivery.
- Ureaplasmal lipoprotein also induce apoptosis, and it is possible that the apoptotic cells sustain genital tract inflammation which promote preterm delivery.
- Studies have also shown a higher rate of vaginal colonization by Ureaplasma species in women with preterm deliveries compared to those with full-term deliveries.
Neonatal infection and the role of Ureaplasma species
- Ureaplasma urealyticum and U. parvum are the most common organisms isolated from infected amniotic fluid and placenta, suggesting the potential role of Ureaplasma species in the development of disseminated neonatal infection.
- The infection is commonly acquired via vertical transmission by three main mechanisms:
- Maternal placental infection with umbilical vessels involvement result in the hematogenous dissemination of infection in the neonate.
- Passage of the organism into the fetal lung via an infected amniotic fluid.
- Perinatal acquisition of infection following passage of the baby through an infected maternal birth canal.
- Pneumonitis, bacteremia, or meningitis can occur following stimulation of host inflammatory responses by the organism.
- Preterm neonates are most commonly affected, and very low birth weight (VLBW) infants have been noted to have invasive Ureaplasma infection. Preterm infants weighing <5.5 pounds are nearly four times more likely to develop systemic infection compared to full term infants weighing above 5.5 pounds.
- It has been suggested that severe Ureaplasma infection in VLBW infants may contribute to the development of severe intraventricular hemorrhage.
- There may also be an association between necrotising enterocolitis and Ureaplasma colonization in preterm neonates.
Colonization by Ureaplasma species and its association with urogenital infections in adults
- There is no significant association between Ureaplasma colonization of the lower genital tract and symptomatic urogenital infection in females.
- The detection of Ureaplasma urealyticum and U. parvum in fluid samples obtained from the pouch of Douglas in 60% of women with lower urogenital tract Ureaplasma colonization confirms the fact that asymptomatic infection of the upper genital tract can occur in women following direct ascent of these organisms from the cervix and vagina to the sterile upper reproductive tract.
- Ureaplasma colonization of the genital tract is common following puberty and it is directly related to sexual activity.
- Ureaplasma urealyticum has been detected in men with nongonococcal urethritis, and also in those without nongonococcal urethritis. Some studies conducted in men show there is an association between urogenital colonization by Ureaplasma urealyticum and nongonococcal urethritis. However, the pathogenic role of Ureaplasma urealyticum in nongonococcal urethritis is still not clear.
- Men with higher bacterial load of U. urealyticum (≥5 x 103) in first-void urine were found to have higher leukocyte counts (in their first-void urine sample) and symptomatic urethritis, suggesting there could be a positive correlation between the bacteria load of U. urealyticum and the development of inflammatory responses to the organism.
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- Okogbule-Wonodi AC, Gross GW, Sun CC, Agthe AG, Xiao L, Waites KB; et al. (2011). "Necrotizing enterocolitis is associated with ureaplasma colonization in preterm infants". Pediatr Res. 69 (5 Pt 1): 442–7. doi:10.1203/PDR.0b013e3182111827. PMC 3968774. PMID 21258263.
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- Kasprzykowska U, Elias J, Elias M, Mączyńska B, Sobieszczańska BM (2014). "Colonization of the lower urogenital tract with Ureaplasma parvum can cause asymptomatic infection of the upper reproductive system in women: a preliminary study". Arch Gynecol Obstet. 289 (5): 1129–34. doi:10.1007/s00404-013-3102-7. PMC 3984420. PMID 24318169.
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- Couldwell DL, Gidding HF, Freedman EV, McKechnie ML, Biggs K, Sintchenko V; et al. (2010). "Ureaplasma urealyticum is significantly associated with non-gonococcal urethritis in heterosexual Sydney men". Int J STD AIDS. 21 (5): 337–41. doi:10.1258/ijsa.2009.009499. PMID 20498103.
- Esen B, Gozalan A, Sevindi DF, Demirbas A, Onde U, Erkayran U; et al. (2017). "Ureaplasma urealyticum: Presence among Sexually Transmitted Diseases". Jpn J Infect Dis. 70 (1): 75–79. doi:10.7883/yoken.JJID.2015.258. PMID 27000449.