Long term amniotic fluid ureaplasma colonization with low dose Ureaplasma parvum serovar 3 induces severe, chronic chorioamnionitis

Christine L Knox, Ilias Nitsos, Samantha Dando, Alan H Jobe, Timothy JM Moss, Cameron Hurst, John Newnham

Research output: Contribution to conferenceAbstract


Background: Ureaplasmas are the most prevalent microorganisms in amniotic fluid from preterm births. We compared severity of chorioamnionitis in sheep, after long-term colonization of amniotic fluid with Ureaplasma parvum serovar 3 or serovar 6.

Methods: At 50 days of gestation (d, term=150d) ewes bearing single fetuses received an ultrasound-guided intra-amniotic injection of either: 2x107 colony forming units (cfu: high dose) of U. parvum (serovar 3, n=7; serovar 6, n=8); 2x104 cfu (low dose) of U. parvum (serovar 3, n=6; serovar 6, n=8); or media control, (n=6). At 125d, fetuses were delivered by caesarean section; amniotic fluid and chorioamnion samples were collected for quantitation of ureaplasmas by culture. A chorioamnion sample was fixed and prepared for quantitation of inflammatory cells (H&E), and immunohistochemistry (anti-ureaplasma rabbit antisera, secondary HRP- or Alex Flour 488-labeled antibodies). Sections were viewed by light or confocal microscopy.

Results: Amniotic fluid ureaplasma titers at delivery ranged from 2.77 x 105 to 3.25 x 106 cfu/mL. The highest numbers of ureaplasmas were from low dose serovar 3 pregnancies. All ureaplasma infected/colonized fetal membranes had higher inflammatory cell counts (p<0.05) than controls. Patterns of histologic inflammation differed between inoculate dose and serovar; monocyte and
lymphocyte (not neutrophil) numbers were higher (p<0.05) in chorioamnion after low dose U. parvum serovar 3 than other groups. Inflammatory changes and tissue repair were evident in chorioamnion of these same animals. Immunohistochemistry demonstrated localization of ureaplasmas within chorioamnion, and typical ureaplasma morphology.

Conclusion: The severity of chorioamnionitis induced by ureaplasmas was dose-and serovardependent. The most severe changes were induced by low dose U. parvum serovar 3.
Original languageEnglish
Publication statusPublished - 2015
Externally publishedYes


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