Dose response, infectivity and stillbirths in pregnant guinea pigs inoculated with Listeria monocytogenes
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Listeria monocytogenes is responsible for approximately 2500 cases and 500 deaths of listeriosis each year. Pregnant women are 20 times more likely to develop listeriosis than the general population with adverse pregnancy outcomes including low birth weight, spontaneous abortions, or stillbirths. Objectives of this study were to use pregnant guinea pigs that were orally-exposed to L. monocytogenes to (1) determine the maternal dose that results in placental transmigration leading to fetal tissue infectivity and/or the occurrence of stillbirths, and (2) relate adverse fetal outcomes to maternal fecal shedding, tissue infectivity, and/or liver damage in order to establish a biomarker of exposure. 5 Eleven of 34 dams treated with e 10CFU delivered stillborn pups. L. monocytogenes cells were cultured from placenta, liver, and brain tissue from all stillbirths. The dose adversely 7affecting 50% of the pregnancies was 10 CFU, which is similar to that estimated in humans at 610 CFU.