Based on sequences of four different genes or genetic regions, the previously recognized biovars 1and2 of Ureaplasma urealyticum are now classified as distinct species, i.e., U. parvum (formerly biovar 1 of U. urealyticum) and U. urealyticum (formerly biovar 2).¹  Frequently found in sexually active men and women, Ureaplasma urealyticum is associated with nongonococcal urethritis, pelvic inflammatory disease, infertility and possibly pyelonephritis.^2,3 Pregnant women with colonization of the upper genital tract have greater likelihood of an adverse pregnancy outcome, including low birth weight infants and perinatal pulmonary infection, meningeal infection and bacteremias.^3,4  PCR testing for Ureaplasma urealyticum on second-trimester amniotic fluid can identify risk for preterm labor and delivery,⁴ including neonatal morbidity.³ Ureaplasma urealyticum is not associated with bacterial vaginosis in some groups of women.⁵  Like M. hominis, U. parvum can cause culture-negative, PCR-proved endocarditis which can be fatal if not treated appropriately.⁶  Further studies of the clinical manifestations of U. parvum infection are needed and are possible on urine with a PCR-microtiter plate hybridization method that can specifically detect U. parvum, U. urealyticum, M. genitalium and M. hominis (M. pneumoniae is specifically excluded).⁷  Preliminary data show that urine from men with NGU often contains mycoplasmas or ureaplasmas (M. genitalium and U. urealyticum are most frequent) and infections with two ureaplasmas or one mycoplasma and one ureaplasma are not unusual.⁷

Although U. urealyticum can be difficult to culture (~40% of PCR-positive amniotic fluids are negative for U. urealyticum on culture²), cultures performed in experienced laboratories for selected clinical problems can be valuable, especially when assayed in parallel with specific EIA antibody tests. Highly purified EIA antigens now permit detection of antibodies specific to U. urealyticum in both culture-positive and culture-negative pregnant women without cross-reactivity to other non-ureaplasmal antibodies.⁸ Infants born from culture-positive amniotic fluid and/or with positive surface cultures typically do not show seroresponse for specific IgG antibodies despite maternal seroconversion.⁹ PCR is more sensitive than culture ~95% vs. 91% for detection of U. urealyticum in the respiratory tract of neonates and much faster (24 hrs. vs. ~5 days).^10,11  An association between U. urealyticum infection and development of bronchopulmonary dysplasia is not established.^12,13 Multiplex, quantitative PCRs now permit evaluation of the possible contributions of ureaplasmas and microplasmas to NGU and other diseases.¹⁴ Ureaplasma and Mycoplasma CNS infections of newborns are not characterized serologically or by intrathecal synthesis of specific IgG.^15,16 In patients with so-called U. urealyticum arthritis, PCR techniques afford rapid, specific diagnosis; these observations, however, have not been confirmed^16,17 Both PCR and hybridization analysis are suitable candidates for population monitoring.^18,19 PCR can also identify particular serovars associated with human disease;²⁰ serotyping data can now be integrated with PCR for identification of the 14 serotypes of U. urealyticum which are classified into two biovars^21-23 (cf. above and #2).  Extended spectrum antibiotic prophylaxis reduces post-cesarean delivery endometritis.²⁴