Molecular detection of bacteria from a possible material oral origin in neonatal gastric aspirates obtained from complicated pregnancies

Abstract

It has been suggested that periodontal disease, a disease that affects the supporting tissues of the teeth, represents a risk factor for adverse pregnancy outcomes. Certain oral pathogens possess a demonstrated ability to translocate and invade the amniotic tissues. Once in the amniotic environment, these opportunistic colonisers could then initiate or contribute to a perinatal infection, and in this way be involved in the complications. The overall aim of this study was to determine the presence, and confirm the origin, of suspected maternal oral microbiota in neonatal gastric aspirates (swallowed amniotic fluid) collected due to complications during pregnancy and/or evidence of neonatal sepsis. Non-cultural PCR-based methods directed to the ribosomal encoding genes (rDNA) were applied to analyse neonatal and maternal samples. The use of universal and species-specific primers that target the bacterial 16S rRNA gene allowed identification and quantification of broad-range and specific bacteria to the species level. Sequence comparative analysis of a more variable fragment, the intergenic spacer region located between the 16S and the 23S rDNA, was finally used to compare strains obtained from the neonates and their counterparts in the respective mother’s oral and vaginal samples. Data analysis allowed identification of a range of potential confounding factors for presence of bacteria in the infants, such as vaginal delivery and prolonged rupture of membranes. However, bacteria with a possible oral origin were mostly identified in the neonatal samples in low prevalence and not associated with any particular variable. Quantitative analysis of potential periodontal pathogens demonstrated the presence of Porphyromonas gingivalis (1%) and Fusobacterium nucleatum (16%) in the neonates. F. nucleatum was detected at relatively high levels (mean=4.41E+02 cells/ml); representing up to 50% of the total bacterial load, which strongly supports its possible role in pregnancy complications. Also, F. nucleatum subspecies analysis and comparisons at the strain level suggest the oral cavity as the most likely origin of this infectious agent. This study supports the need for further studies.