Fetal environment and fetal intestine are sterile during the third trimester of pregnancy

Publication date: Available online 26 September 2018Source: Veterinary Immunology and ImmunopathologyAuthor(s): Nilusha Malmuthuge, Philip J. GriebelAbstractRecent next generation sequencing studies on host-associated microbiomes generated debatable conclusions regarding the central dogma of fetal gut sterility. These observations challenge the concepts that microbial colonization of the gut begins during and after birth as well as the concept of antigen-independent prenatal maturation of mucosal-associated lymphoid tissue in ruminants and humans. The placental barrier varies markedly among mammalian species with mice and humans having haemochorial placentas (fetal tissue in direct contact with maternal blood) versus epitheliochorial placentation (maternal and fetal blood separated by six tissue layers) in ruminants. Therefore, this study re-examined the question of fetal gut sterility using the fetal lamb as a model ruminant species with the most complete placental barrier. Use of PCR and quantitative real-time PCR with three different pairs of universal bacterial primers (27 F and 1492R, HDA1 and HDA2, U2F and U2R) to amplify 16S rRNA gene did not generate detectable PCR products from samples collected from the fetal environment (placenta, amniotic fluid) and fetal intestine during the third trimester of pregnancy. Procedures to further enrich microbial DNA from total extracted DNA also resulted in no detectable genomic DNA. Moreover, use of 16S amplicon sequencing confir...
Source: Veterinary Immunology and Immunopathology - Category: Veterinary Research Source Type: research