MECHANISMS INVOLVED IN THE ADAPTATION OF ESCHERICHIA COLI O157:H7 TO THE INTESTINAL MICROENVIRONMENT

PALERMO, MARINA S.; IBARRA, CRISTINA; BRUBALLA, ANDREA; GALLY, DAVID; RAMOS, MARIA VICTORIA; GOMEZ, MARTIN; MCATEER SP; PINEDA, G; FERNANDEZ BRANDO, ROMINA

Bernal

Jornada; Primera Jornada Argentina de ncRNA; 2017

RNA group, Universidad Nacional de Quilmes, Universidad de Buenos Aires Facultad de Medicina.

Although the productionof Shiga toxin by enterohemorragic Escherichiacoli (EHEC) determines Hemolytic Uremic Syndrome (HUS) onset, factors thatmodulate intestinal colonization are key components in pathogenesis and hostmucosal immune response. We showed previously that the passage of a clinicallyisolated EHEC strain (125/99) through the gastrointestinal tract of miceincreases its pathogenicity in mice, and that stool-recovered strains (125R and125RR) induce a more generalized and persistent colonization than the parentstrain (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.