Study of the intestinal mucosal innate immune response in a mouse model of Hemolytic Uremic Syndrome (HUS) by intragastrical inoculation of Shiga-toxin-producing Escherichia coli (STEC).

A BRUBALLA, ; PALERMO MS.; R FERNANDEZ-BRANDO; MV RAMOS, ; G PINEDA,

Mar del Plata

Congreso; Reunión Anual de la SAI/SAIC/SAFIS; 2018

SAI

MECHANISMS INVOLVED IN THE ADAPTATION OF ESCHERICHIA COLI O157:H7 TO THEINTESTINAL MICROENVIRONMENT MECANISMOS INVOLUCRADOSEN LA ADAPTACIÓN DE ESCHERICHIA COLIO157:H7 AL AMBIENTE INTESTINAL RominaFernandez-Brando (1), Martín Gómez (1), Andrea Bruballa (1), Gonzalo Pineda(1), Maria Victoria Ramos (1), Cristina Ibarra (2), Sean McAteer (3), DavidGally (3), Marina Palermo (1). (1)Laboratorio de Patogénesis e Inmunología de Procesos Infecciosos, Instituto deMedicina Experimental (IMEX)-CONICET, Academia Nacional de Medicina.(2) Laboratoriode Fisiopatogenia, Facultad de Medicina, UBA, Buenos Aires, Argentina.(3) Division of Infection and Immunity, TheRoslin Institute, University of Edinburgh. Although the production of Shiga toxin by enterohemorragic Escherichia coli (EHEC) determinesHemolytic Uremic Syndrome (HUS) onset, factors that modulate intestinalcolonization are key components in pathogenesis and host mucosal immuneresponse. We showed previously that the passage of a clinically isolated EHECstrain (125/99) through the gastrointestinal tract of mice increases itspathogenicity in mice, and that stool-recovered strains (125R and 125RR) inducea more generalized and persistent colonization than the parent strain(Fernandez-Brando et al, 2012). We aimed at elucidating the underlyingmechanism involved in the pathogenesis and bacterial adaptation to theintestinal environment of mice. We assessed the global transcription profile bymicroarray and found more than 100 differentially expressed genes in 125RRstrain: small RNAs (sRNA), proteins from the type three secretion system,several enzymes, membrane transporters and receptors and several putativetranscripts. We confirmed the augmented expression of EspB and fliC (p<0.05)and the diminished expression of ECs1537/1561 (p<0.05) by qPCR. We alsodemonstrated the augmented expression of EspD by western blot, which couldexplain the greater colonization of stool-recovered strains. In an attempt toelucidate targets for sRNA regulation we studied acid resistance mechanisms,since arcZ, rprA, and ryhB are involved in that mechanism. The 125RR strainshowed an increased survival at pH 2.5 for 1 h (p<0.05), which coulddetermine a lower infectious dose. Given the importance of motility in surpassingthe mucus barrier in the mucosal environment and the finding of the augmentedexpression of flic, we tested the motility phenotype in semisolid agar. The125RR strain showed an increased motility compared to 125/99 and 125R (p<0.01).These results suggest that the stool-recovered strain is more proficient todeal with the murine mucosal barrier thus leading to the onset of HUScharacteristic symptoms in mice.