13 - Development of an Ascending Model of Infection and Preterm Birth
Thursday, January 28, 2021
5:00 PM – 5:15 PM EST
Objective: Microbial invasion of the intraamniotic cavity (MIAC) and intraamniotic inflammation (IAI) are factors associated with spontaneous preterm birth (PTB). Understanding the route of infection, site of colonization and mechanisms of host inflammatory response is critical to reduce PTB risk. Although multiple models have been reported, reproducible evidences are lacking to determine route of MIAC and kinetics of ascension. This study developed an ascending model of infection and PTB with live bacteria (E. coli) in pregnant mice.
Study Design: Two independent experiments were conducted: 1. To determine E. coli induced PTB, CD-1 mouse were injected with three different doses of E. coli (103, 106, and 1010 colony forming units[CFU]) 25 µl of either E. coli in liquid broth (LB; control) or LB alone (control) was administrated into the vagina on embryonic day (E)15 using a 200-L pipette tip. PTB (defined as delivery before E18.5) was monitored using live video, and 2) To determine the kinetics and colonization, 1010 CFU/ml (colony forming unit/ml) E. coli labeled with 10 µM carboxyfluorescein succinimidyl ester (CSFE) was vaginally administered. Mice were sacrificed at 6h, 24h and 48h and various tissues were collected. 10 µm frozen section were counter-stained with DAPI and microscopically analyzed to check E. coli trafficking in uterine tissues.
Results: Compared to LB injected animals (controls), vaginal administration of 1010 CFU E. coli resulted in 71% (5/7) PTB within 48 hours. Lower doses (103 and 106 CFU) produced PTB (25% [1/4] and 50% [2/4]) respectively indicating dose effect. CFSE labelled E. coli was localized in the cervix (6 hrs), uterine decidua and placental/decidual interface (24 hrs) and in fetal membranes (48 hrs) determining the kinetics (Fig 1).
Conclusion: Our model can be used to study MIAC and IAI. Kinetics of localization in various tissues suggest path of ascension. Host inflammatory activation is being determined in areas of colonization. Besides providing a model for studying infection and PTB, this can test effective ways of reducing PTB.