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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
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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.
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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.
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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.
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Genitourinary
Infection
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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