SHIGA TOXIN-PRODUCING Escherichia coli O157:H7 SHOWED INCREASED PATHOGENICITY IN THE MICE AFTER THE PASSAGE THROUGH THE GASTROINTESTINAL TRACT OF THE SAME HOST

FERNANDEZ BRANDO, ROMINA J; MILIWEBSY, ELIZABETH; CABRERA, G; BASCHIERK, ARIELA; RAMOS, MARIA VICTORIA; RIVAS, M; PALERMO, MARINA SANDRA

Ghent

Congreso; ECMIS 2011-Ghent. E. coli and the Mucosal immune System: Interaction, Modulation and Vaccination; 2011

SHIGA TOXIN-PRODUCING Escherichia coli O157:H7 SHOWED INCREASED PATHOGENICITY IN THE MICE AFTER THE PASSAGE THROUGH THE GASTROINTESTINAL TRACT OF THE SAME HOST   Authors & affiliations: FERNANDEZ-BRANDO, RJ (1); MILIWEBSKY, E (2); CABRERA, G (1); BASCHKIER, A (2); RAMOS, MV (1); RIVAS, M (2); PALERMO, MS (1). (1) División Inmunología, Academia Nacional de Medicina; (2) Servicio Fisiopatogenia, Instituto Nacional de Enfermedades Infecciosas - ANLIS “Dr. Carlos G. Malbrán”, Buenos Aires, Argentina. mspalermo@hematologia.anm.edu.ar   Abstract:  (Your abstract must use Normal style and must fit in this box.  Your abstract should be no longer than 300 words. Hemolytic Uremic Syndrome (HUS) is a rare but life-threatening complication of Shiga-toxin (Stx) Escherichia coli (STEC) infections, characterized by acute renal failure, thrombocytopenia and hemolytic anemia. Epidemiological data indicate that the horizontal transmission of certain pathogens requires significantly lower doses than those used with laboratory-cultured bacteria. The aim of this work was to study how affect the pathogenicity of  a STEC strain in the mouse,   the passage through the gastrointestinal tract (GIT) of the same specie. Therefore, we inoculated weaned mice with a STEC strain isolated from a HUS patient (parental strain) and we recover this strain directly from the feces after one passage (125r) or two passages (125rr) through the GIT of the mouse. We confirmed the phylogenetic identity of the 125r and 125rr (stool-recovered strains) with its parental strain by using the pulsed field gel electrophoresis and we observed no significant differences. Although we observed a four fold reduction in the production of Stx by the stool-recovered strains, the mortality rates of 2x108 CFU/kg of each strain determined a similar mortality around  30%. All dead animals showed renal failure signs. Bacterial elimination in stools and adherence to the intestine from inoculated mice revealed a higher level of colonization in those animals inoculated with the stool-recovered strains (median, rank [CFU/g feces]) (Stools 72 h: parental strain= 30; 0-2.4x105, 125r= 2400; 0-8.3x1010, 125rr= 1.5x106, 0-2x1011; p<0.01 125r and 125rr vs parental strain, Wilcoxon test). In addition, 125rr strain was able to induce mortality (14%) even with an inoculum of 1x104 CFU/kg, whereas the same  inoculum of parental strain did not induce any death . These results indicate that stool-recovered strains presented an increased pathogenicity in the mice, probably associated to an increased ability to colonize the mice intestine.