Distribution of , , , and Resistance Genes in the Vaginal Ecosystem of Women during Pregnancy and Puerperium.

The inhabitants of the vaginal ecosystem can harbor genetic determinants conferring antimicrobial resistance. However, detailed data about the distribution of resistance genes in the vaginal microbiome of pregnant women are still lacking. Therefore, we assessed the presence of macrolide (i.e., genes) and tetracycline (i.e., genes) resistance markers in the vaginal environment of Caucasian women at different gestational ages. Furthermore, the detection of resistance genes was related to the composition of the vaginal microbiota. A total of 228 vaginal samples, collected at different trimesters of pregnancy or during the puerperium, were tested for the presence of , , , and by in-house end-point PCR assays. The composition of the vaginal microbiota was assessed through a microscopic evaluation (i.e., Nugent score) and by means of sequencing V3-V4 hypervariable regions of the bacterial 16 rRNA gene. Overall, the most detected resistance gene was (76.7%), followed by (55.2%). In 17% of women, mainly with a 'normal' vaginal microbiota, no resistance genes were found. Except for , a significant correlation between the positivity of resistance genes and a dysbiotic vaginal status (i.e., bacterial vaginosis (BV)) was noticed. Indeed, samples positive for at least one resistance determinant were characterized by a decrease in spp. and an increase of BV-related genera (). A high predominance of vaginal spp. (>85%) was associated with a lower risk of gene detection, whereas the presence of (>1%) increased the risk of positivity for all analyzed genes. Different types of vaginal microbiota are associated with peculiar resistance profiles, being a lactobacilli-dominated ecosystem poor in or free of resistance genes. These data could open new perspectives for promoting maternal and neonatal health.