Assessment of human placental microbial signatures in pre-eclampsia using shotgun metagenomics

This study evaluated the presence of bacterial species in the placenta of women with pre-eclampsia and compared with that of normotensive women. One hundred and twenty participants, comprising 60 pre-eclamptic (30 early- and late-onset, respectively) and 60 age-matched normotensive women (30 early and late-gestation normotensive, respectively) were recruited. After informed consent was obtained, the placenta were obtained through caesarean section with sterile and standardized clinical procedures. DNA was extracted from each tissue, and the samples were pooled into six libraries and sequenced on Illumina NextSeq500 using a shotgun metagenomic approach. Bioinformatics was used to analyse the reads with the implementation of Kraken2/MetaPhlAn classification methods and complemented by multi-layered contamination assessment strategy that included frequency-based decontam filtering. Most reads were classified as belonging to the phyla Cutibacterium acnes, Staphylococcus epidermidis, and various Bradyrhizobium species. PE samples showed notable Corynebacterium tuberculostearicum and Pseudomonas species, while Bradyrhizobium and Cutibacterium acnes dominated normotensive samples. Further analysis showed no significant difference between bacterial species of pre-eclamptic and normotensive placental samples. The results show very low levels of bacteria in the placental samples. In addition, a little difference was observed between the bacterial compositions of pre-eclamptic and age-matched normotensive placental tissues, but not statistically significant.