Intra-amniotic infection and latent vaginal colonisation with Ureaplasma spp. are frequently associated with preterm birth (PTB). Two species of Ureaplasma are known to infect humans, Ureaplasma parvum and Ureaplasma urealyticum. These are comprised of 14 genotypes, four representing U. parvum and 10 representing U. urealyticum. Clinically, U. parvum is most common; however, it is not known why colonisation results in PTB in some cases and not others.
Recently, we developed a novel high-resolution melt (HRM) PCR assay to detect and distinguish the four genotypes of U. parvum in a single step. In this subsequent study we have applied this assay to vaginal swabs from a cohort of pregnant women to uncover any association between specific U. parvum genotypes and PTB.
206 women were recruited between 13-26 weeks gestation. Vaginal swabs were provided at three time points. These were analysed by culture and real-time PCR for Ureaplasma spp. Positive samples were genotyped using our HRM assay. Associations between vaginal colonisation status, U. parvum genotype and an outcome of PTB were detected using chi-square analyses.
To date we have pregnancy outcome data on 151 women. Thirteen women delivered preterm (8.6%). Ten (77%) were colonised with Ureaplasma spp. compared to 57/138 (41%) from term pregnancies. For preterm cases this represented eight instances of U. parvum, one of U. urealyticum and one of both species. For U. parvum, genotype SV6 was detected on seven (78%) occasions and there was one case each of SV1 and SV3 detected. From term pregnancies, 48 cases of U. parvum were detected, representing seven, 18 and 21 cases of SV1, SV3 and SV6 respectively. Two cases were unable to be genotyped.
Our preliminary results suggest a significant association exists between vaginal colonisation by Ureaplasma spp., specifically U. parvum and PTB. An association between U. parvum SV6 and PTB also seems likely, however, at present, numbers in the PTB group are too small to show any significance.