Cytotoxic effects in human colon induced by E. coli O113:H21 expresing Shiga toxin type 2 and Subtilase

GERHARDT ELIZABETH; MASSO MARIANA; ZOTTA ELSA; AMARAL MARÍA MARTA; IBARRA CRISTINA

New Delhi

Simposio; Malnutrition, Gut-Microbial Interactions and Mucosal Immunity to Vaccines; 2011

Keystone Symposium

Shiga toxins-producing Escherichia coli (STEC) strains are responsible for intestinaldisease and hemolytic uremic syndrome (HUS). STEC O157:H7 is by far the mostprevalent serotype associated with HUS although STEC non-O157 strains isolatedfrom children with HUS drastically increased during the past ten years. In Argentina,the main virulence factor of STEC is the Shiga toxin type 2 (Stx2) present in strainsO157 and non-O157. Recently, it have been reported that some STEC non-O157and, among them the serotype O113:H21, produce other cytotoxin named Subtilase(SubAB) which may contribute to the pathogenesis of HUS. The purpose of thepresent study was to examine the physiological and morphological effects of STECO113:H21 on human colonic mucosa by the Ussing chamber technique in orderto better understand the mechanisms by which STEC non-O157 induces diarrhea.We have used O113:H21 STEC strain 98NK2 isolated from a patient with HUS andderivatives of this STEC strain with mutations in either stx2 (98NK2Δstx2) or subABgenes (98NK2ΔsubAB) kindly provided by Dr James Paton, University of Adelaide,Adelaide, Australia. Bacteria grown to exponential phase and added to the mucosalside of the colonic mucosa caused an inhibition of the absorptive net water flux(Jw) recorded automatically by a special electro-optical device. Both, 98NK2 and98NK2ΔsubAB strains showed an inhibition of Jw that was already significant after 60min. The 98NK2Δstx2 also inhibited the Jw in a time-dependent manner. This effect,less marked than that registered with the 98NK2ΔsubAB, suggests that Stx2 affectmore than SubAB the normal water absorption. Histopathology of colonic mucosatreated with 98NK2 and 98NK2ΔsubAB revealed destruction of the upper third ofthe colonic mucosa with the presence of hemorrhagic areas. On the other hand,98NK2Δstx2 strain destroyed the surface epithelium, decreased of globet cells andproduced a moderate infiltration of neutrophils. This is the first study showing thatStx2 and SubAB produced by a strain of STEC O113:H21 could participate in themechanisms of diarrhea.