Fusobacterium nucleatum (Fn) is one of the most abundant species in the sub-gingival biofilm and has been isolated from amniotic fluid in cases of adverse pregnancy outcomes (APO). The aim of this study was to determine whether experimentally induced periodontitis using Fn and Porphyromonas gingivalis increases APO in mice and whether particular sub-species of Fn were capable of translocating from the periodontium to the murine placenta haematogenously.
Periodontitis was induced in mice using a mixture of Fn and P. gingivalis and mice were mated and bacterial inoculations continued until day 18 of their 21 day gestation.
Alternatively, at day 16, pregnant mice were intravenously injected with 0.1 mL saline or individual Fn subspecies.
Mice were euthanased and the placenta, liver, spleen and blood extracted and maternal weight, litter size, number of viable fetuses, number of resorptions, fetus weight and placenta weight recorded. Samples were assessed for Fn presence using PCR.
Alveolar bone loss was assessed using stereomicroscopy.
a) Mice with alveolar bone loss demonstrated significantly higher fetal weights and fetal/placental weight ratios. There were no significant differences in maternal weights, placental weights, litter size, number of resorptions or number of viable fetuses. PCR analysis did not identify Fn in the placenta, blood, liver or spleen of any experimental mouse showing alveolar bone loss.
b) Mice injected intravenously with Fn demonstrated intrauterine growth restriction, low birth weight and fetal resorption. The litter size and number of resorptions were statistically significant between groups, (p=0.023 and p=0.001 respectively). Fn subsp. nucleatum was the only subspecies found to migrate haematogenously to the uterus.
This study confirmed that Fn can transmigrate haematogenously to the uterus, leading to APO in mice. However induced periodontitis in mice was not associated with placental colonization of Fn, but led to an increase in fetal weight and the fetal weight/placental weight ratio, suggesting an increased efficiency of the placenta.