The Effect of Antibiotics on Shiga toxin Phage Movement in Ruminants

Shiga toxin-producing E. coli (STEC) such as E. coli O157:H7 are important emerging pathogens in the United States. Following intestinal infection, the production of Shiga toxins by STEC results in serious and life-threatening complications. The genes encoding these potent toxins are present on viral particles known as bacteriophages. We have previously found that when mice are infected with O157 treating them with certain antibiotics leads to an increase in toxin expression. The antibiotics also lead to increased movement of the viruses from the O157 strain into other E. coli in the mouse intestine. Our hypothesis is that certain antibiotics used in agriculture lead to increased movement of toxin genes carried by the viruses from one bacterial strain to another in the intestine of farm animals such as sheep and cattle. Our project will examine the effects of antibiotics used in agriculture on the movement of labeled toxin bacteriophages in the intestines of sheep. If this occurs in farm animals it is not only a critical issue that has to be considered in the use of certain antibiotics, but may go a long way in explaining the emergence of Shiga toxin positive O157 and other STEC serotypes. By understanding more about the variations between different Shiga toxin-encoding bacteriophages and learning what drives them to move from one strain to another we will be better placed to prevent the spread of bacteriophages and the potential evolution of a Shiga toxin-producing organism even more deadly than E. coli O157: H7.