Zinc has been shown to reduce the duration and severity of diarrheal diseases in studies of poor children on several continents. Although these beneficial effects of zinc were first attributed to correction of a zinc deficiency in malnourished children, studies have shown beneficial zinc effects even in children with normal serum zinc levels before study. Studies of enteric pathogens in healthy experimental animals and cultured cell assays have also shown protective effects of zinc in non-zinc deficient animals or conditions. In our laboratories we discovered that zinc strongly inhibits the production of several important virulence factors human enteropathogenic E. coli strains in vitro. We then extended those observations to rabbit EPEC strains and found similar results. Rabbits are natural hosts for EPEC infection, so they constitute a good animal model for us to test zinc efficacy in vivo. Now we also have in vitro data showing that zinc also inhibits virulence in Shiga-toxigenic E. coli (STEC, also known as enterohemorrhagic E. coli, or EHEC). In human-derived EPEC, rabbit EPEC, and STEC, zinc decreases the bacterial production of virulence factors, including adhesins, secreted effector proteins and Shiga toxin (Stx). We propose to further examine the effect of zinc on A/E E.coli infections both in vitro and in vivo. There are 3 specific aims:
Specific Aim 1 : Determine the direct effects of zinc on attaching and effacing E. coli (including EPEC, REPEC and STEC) in vitro under different growth conditions (and in the presence of antibiotics).
Specific Aim 2. : To confirm and further define the effects of zinc on A/E E.coli infection in vivo in ligated rabbit ileal loops, and to examine its effect on STEC infections in these loops.
Specific Aim 3 : Determine if zinc administration in vivo can protect rabbits against orogastric infections with REPEC and STEC. In addition to examining the effects of zinc on clinical disease course and intestinal pathology, we will also examine if zinc can protect against extra-intestinal pathology induced by STEC (especially kidney damage). For these studies we will use a new model of hemorrhagic colitis (HC) and hemolytic uremic syndrome (HUS) which develops in Dutch Belted rabbits challenged with REPEC strains expressing Stx1 or Stx2.
""""""""Attaching and Effacing E. coli"""""""" includes 2 groups of diarrhea-producing E. coli, enteropathogenic E. coli (EPEC) and enterohemorrhagic E. coli (EHEC, also called Shiga toxigenic E. coli, or STEC). EHEC, such as strain O157:H7, has received wide publicity due to foodborne outbreaks. Zinc inhibits the virulence of both of these groups of E. coli, and we wish to study zinc further to see if it could be used as a treatment for these infections.
