Strain level variation in Lactobacillus jensenii isolated from preterm and full-term pregnancies

Each year, 15 million infants are born preterm ( before 37 weeks gestation), and this is the leading cause of mortality for children under the age of five. Whilst there is no single cause, factors such as maternal genetics, environmental interactions, and the vaginal microbiome have been associated with an increased risk of preterm birth. Previous studies show that a vaginal microbiota dominated by Lactobacillus is, in contrast to communities containing a mixture of genera, associated with full term birth. However, this binary principle does not fully consider more nuanced interactions between bacterial strains and the host. Here, through strain-level analysis, we identify a subgroup of L. jensenii strains from preterm pregnancies that are phylogenetically distinct to strains from full-term pregnancies. We further explore this phenomenon using metagenome-assembled genomes and sequencing of cultured isolates.