Presence of Shiga toxin producing Escherichia coli in endocervix of asymptomatic pregnant women from Argentina

SCALISE M.LUJAN; PORPORATO, MELINA; GARIMANO, NICOLAS; LEONINO, PATRICIA; PEREYRA, ADRIANA; FERREIROS, JOSE A.; CASALE, ROBERTO; AMARAL M MARTA; IBARRA, CRISTINA; SACERDOTI, FLAVIA

Virtual

Congreso; International Federation of Placenta Associations (IFPA2021); 2021

International Federation of Placenta Associations (IFPA2021)

Objective: The aim of this study was to detect virulence factor genes from Shiga toxinproducing E. coli (STEC) in the endocervix from asymptomatic pregnant women and toshed light on the possible role of STEC as a pathogen responsible for adversepregnancy outcomes.Methods: Endocervical swabs were collected from 103 pregnant women (12 to 30weeks of pregnancy) from Hospital Posadas, Buenos Aires, Argentina, during theirantenatal examination. Swab samples were enriched in Tryptic Soy Broth (TSB)overnight at 37°C and then streaked into Sorbitol MacConkey agar. E. coli colonieswere confirmed by identification of the uidA gene by PCR. Then, E. coli positivesamples were analyzed for STEC virulence factors genes: stx1, stx2, eae, rfb O157 ,lpfA O113 and hcpA. E. coli samples that were positive for stx2 gene detection weregrown in Luria-Bertani Broth (LB) by Shiga toxin type 2 (Stx2) cytotoxicity evaluation.For that, bacterial supernatants were filter-sterilized and cytotoxicity was evaluated onVero, Swan 71 and HeLa cell lines.Results: Our results showed that 14.5% of the samples were positive for E. coli (uidApositive gene). Furthermore, 9/15 (60 %) of the E. coli-positive samples carried thestx2 gene and 6/15 (40 %) carried the lpfA O113 and hcpA genes. Bacterial supernatantfrom an E. coli-positive endocervical sample carrying stx2 gene exhibited high cytotoxicactivity on Vero, Swan 71 and HeLa cells. Stx2 identity was confirmed by cytotoxicityneutralization with an anti-Stx2 monoclonal antibody.Conclusions: The main finding of this work was to identify STEC in the endocervicalmicrobiota of asymptomatic pregnant women. Additionally, we demonstrated thatSTEC can secrete Stx2 with a high cytotoxic activity on human extravillous trophoblast(Swan 71) cells and endocervical (HeLa) cells. These results open a new perspectivewith respect to the possible role of STEC in the reproductive health of women.