Presence of Shiga toxin producing Escherichia coli in endocervix of asymptomatic pregnant women: Novel pathogen responsible for adverse pregnancy outcomes?

PORPORATO, M; SCALISE, ML; IBARRA, C; SACERDOTI, F

Congreso; REUNIÓN DE SOCIEDADES DE BIOCIENCIAS 2020; 2020

E. coli can colonize the vagina, usually asymptomatically, although epidemiologic studies have showed that the presence of this bacterium in the endocervix microbiota could be a risk factor for pregnancy.We have previously reported that Shiga toxin (Stx) producing E. coli (STEC) infections during pregnancy may cause maternal or fetal damage mediated by Stx2 in rats in early or late stage of gestation.The goal of this study was to detect STEC in the endocervix from asymptomatic pregnant women. Endocervical swabs from 103 asymptomatic pregnant women with gestational age of 12 to 30 weeks from the National Hospital Posadas were enrolled. Swab samples were enriched in Tryptic Soy Broth and then streaked on sorbitol-MacConkey (SMAC) agar. E. coli was confirmed by the presence of uidA gene detected by polymerase chain reaction PCR. The positive samples for E. coli were analyzed for STEC virulence factors genes such as: stx1, stx2, eae, rfbO157, lpfAO113 and hcpA genes. The stx2 positive E. coli samples were grown in Luria-Bertani Broth and the filter-sterilized bacterial supernatants (SN) were used to evaluate Stx2 activity on Vero, Swan and Hela by cell viability assay. Our results showed that 14.6% (15/103) of the endocervical samples were positive for uidA gene. Additionally, we found that 8.7% (9/103) was positive for stx2 and 5.8 % (6/103) for lpfAO113 and hcpA genes. The SN of one of them expressing stx2 gene had a high cytotoxic activity on Vero, Swan 71 and HeLa cells. Stx2 identity was checked using an anti-Stx2 antibody in order to neutralize the cytotoxic effects. In conclusion, we demonstrate that STEC can be asymptomatically present in the endocervix and that can potentially express Stx2. This study may open a new perspective to understand whether STEC can be a novel pathogen involved in adverse pregnancy outcomes.