Porphyromonas gingivalis fimA mutant in a rodent model of infection

Porphyromonas gingivalis is one of the primary pathogens in periodontitis, a disease recently associated with adverse pregnancy outcomes. We have reported the development of an animal model that can be used to study the differences in virulence among P. gingivalis strains during pregnancy. Fimbriae, an important virulence factor of P. gingivalis, are required for attachment to and invasion of epithelial and endothelial cells. Our hypothesis is that the presence of fimbriae is important in colonization of fetal units and contributes to the disease. Objective: This study was design to compare P. gingivalis 33277 with its fimbriae deficient mutant (fimA) to further understand the importance of fimbriae in the colonization of placenta and fetal tissue. Methods: Three groups of pregnant rats were intravenously inoculated at day 14 of gestation with sTSB (control) or 10⁹ CFU/ml of either P. gingivalis 33277 or the fimA mutant. Necropsy was performed at gestation day 20. Maternal and fetal tissues were collected to determine the extent of colonization by P. gingivalis using culture and PCR techniques. Histological analysis of placental tissue was used to compare the amount and type of lesions caused by the wild-type and the mutant. Results: No significant differences were detected by PCR or culture techniques in the colonization of maternal and fetal tissues between rats infected with the wild-type or the fimA mutant. However, qualitative differences in the host inflammatory response were observed in the endometrium, placenta and umbilical tissue. Conclusion: Fimbriae do not appear to be of primary importance for intrauterine colonization by P. gingivalis, although a significant difference in the host inflammatory response was detected. This Research was supported by a UFCD Student Summer Research Fellowship, the Center for Molecular Microbiology, the NIH-NIDCR grant DE007200, and a UFCD Seed Grant.