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Shepard first described Ureaplasma urealyticum in 1954 after recovery of these organisms from male patients with nongonococcal urethritis.1 Initially referred to as T-strain (“tiny strain”) mycoplasma, these pleomorphic organisms measure less than 500 nm in diameter, lack a cell wall, and are classified as members of the family Mycoplasmatacea.2Ureaplasma differ from other Mycoplasmatacea in that they produce urease and therefore are capable of generating adenosine triphosphate from hydrolysis of urea. This activity serves as the primary energy source for Ureaplasma. Ureaplasma urealyticum has historically been subtyped into 14 serovars. However, recent molecular characterization of these serovars has resulted in a reclassification of U urealyticum into 2 distinct species: U parvum (serovars 1, 3, 6, and 14) and U urealyticum (serovars 2, 4, 5, and 7–13).3


Ureaplasma spp are found on the cervical or vaginal mucosal surfaces of the majority of asymptomatic women and may therefore be considered commensal organisms of the adult female genital tract.4 Colonization of the male urethra has also been described, although it appears to occur less frequently. Although they may colonize in the absence of symptoms or pathology, there is ample evidence implicating Ureaplasma as the primary etiologic agent in a variety of urogenital diseases in both men and women.

Mucosal colonization with Ureaplasma occurs less commonly in adolescents and young children than in adults and increases in frequency with the onset of sexual activity. Vertical transmission of Ureaplasma with resulting mucosal colonization of the neonate occurs commonly (> 10% of births to colonized mothers), is increased in frequency in the setting of prolonged rupture of membranes and low birth weight, and may persist for several months postnatally.

Ureaplasma spp produce a number of virulence factors including immunoglobulin A protease, phospholipases A and C, hydrogen peroxide, NH3, and the more recently recognized hemolysins.4 Phospholipases may be of particular importance as they are hypothesized to play a role in the development of preterm labor in colonized, pregnant women by liberating arachidonic acid and increasing prostaglandin synthesis.

Clinical Features

Genitourinary Infection

Ureaplasma spp may cause urethritis in both men and women. Ureaplasma urealyticum in particular is frequently isolated from male adolescent and adult patients with nongonoccal urethritis. Epididymitis and prostatitis secondary to U urealyticum have also been described.5,6 The presence of Ureaplasma in the urinary tract has been linked to local formation of stones, possibly mediated by urease activity. Colonization and/or infection of the female genital tract are associated with numerous obstetrical complications including infertility, spontaneous abortion, chorioamnionitis, preterm labor, and postpartum endometritis.2,4,7 It is important to note that Ureaplasma are capable of invading the intrauterine space including the maternal–fetal membranes and are the most common organisms isolated from amniotic fluid, infected placentas, and neonatal cord blood.8,9

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