MECHANISMS INVOLVED IN THE ADAPTATION OF Escherichia coli O157:H7 TO THE MURINE INTESTINAL MICROENVIRONMENT

BRUBALLA, ANDREA CECILIA; GALLY, DAVID; FERNÁNDEZ BRANDO, ROMINA JIMENA; PINEDA, GONZALO EZEQUIEL; PALERMO, MARINA SANDRA; MCATEER, SEAN; RAMOS, MARIA VICTORIA

Florencia

Simposio; VTEC 2018; 2018

Società Italiana di Diagnostica di Laboratorio Veterinaria (SIDiLV)

Although the production of Shigatoxin by enterohemorrhagic 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 the same host. This mouse-adapted strain (125RR)induces a more generalized and persistent colonization than the parent strain,together with the induction of HUS symptoms and mortality with theadministration of suboptimal innocula (Fernandez-Brando et al, 2012). We aimed toelucidate the underlying mechanism(s) involved in the patho-adaptation of thisstrain to the intestinal environment of mice. We assessed the globaltranscription profile by microarray. Specific transcript level changes wereconfirmed by qPCR. Acid resistance and motility were measured using standardtechniques. We 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 also demonstrated the augmented expression of EspD by Westernblot, which could explain the greater colonization of stool-recovered strains. Inan attempt to elucidate targets for sRNA regulation we studied acid resistancemechanisms, since arcZ, rprA, and ryhB are involved in that mechanism. The125RR strain showed an increased survival at pH 2.5 for 1 h (p<0.05), whichcould determine a lower infectious dose. Given the importance of motility insurpassing the mucus barrier in the mucosal environment and the finding of theaugmented expression of flic, wetested the motility phenotype. The 125RR strain showed an increased motilitycompared to 125/99 (p<0.01). We conclude that the strain hasadapted to deal with the murine mucosal barrier with regulatory changes thatalter colonization, motility and acid resistance; this understanding mayindicate the bacterial mechanisms that are required for horizontal transmissionof these zoonotic pathogens in their animal and human populations.