ASSESSMENT OF THE MECHANISMS INVOLVED IN HOST ADAPTATION OF ENTEROHEMORRAGIC ESCHERICHIA COLI (EHEC).

ROMINA J FERNÁNDEZ BRANDO; PINEDA, G; MCATEER SP; MARTÍN M GÓMEZ; RAMOS MV; GALLY, DAVID; BRUBALLA, A; IBARRA, C; PALERMO, MARINA S

Mar del Plata

Congreso; LXI Reunión Científica Anual de la Sociedad Argentina de Investigación Clínica-LXIV Reunión Anual de la Sociedad Argentina de Inmunología-XLVIII Reunión Anual de la Sociedad de Argentina de Farmacología Experimental-VII Reunión Científica Anual de la Soci; 2016

SAIC-SAI-SAFE

Although the production of Shiga toxin by enterohemorragicEscherichia coli (EHEC) determines Hemolytic Uremic Syndrome(HUS) onset, factors that modulate intestinal colonization are keycomponents in pathogenesis and host mucosal immune response.We showed previously that the passage of a clinically isolated EHECstrain (125/99) through the gastrointestinal tract of mice increasesits pathogenicity in mice, and that stool-recovered strains (125Rand 125RR) induce a more generalized and persistent colonizationthan the parent strain (Fernandez-Brando et al, 2012). Weaimed at elucidating the underlying mechanism involved in the pathogenesis and bacterial adaptation to the intestinal environmentof mice. We assessed the global transcription profile by microarrayand found more than 100 differentially expressed genes in 125RRstrain: small RNAs (sRNA), proteins from the type three secretionsystem, several enzymes, membrane transporters and receptorsand several putative transcripts. We confirmed the augmentedexpression of EspB and fliC (p<0.05) and the diminished expressionof ECs1537/1561 (p<0.05) by qPCR. We also demonstratedthe augmented expression of EspD by western blot, which couldexplain the greater colonization of stool-recovered strains. In anattempt to elucidate targets for sRNA regulation we studied acidresistance mechanisms, since arcZ, rprA, and ryhB are involved inthat mechanism. The 125RR strain showed an increased survivalat pH 2.5 for 1 h (p<0.05), which could determine a lower infectiousdose. Given the importance of motility in surpassing the mucus barrierin the mucosal environment and the finding of the augmentedexpression of flic, we tested the motility phenotype in semisolid agar.The 125RR strain showed an increased motility compared to 125/99and 125R (p<0.01). These results suggest that the stool-recoveredstrain is more proficient to deal with the murine mucosal barrierthus leading to the onset of HUS characteristic symptoms in mice.