Can your dog give your baby e. coli bacteria or virus?

The scenario I am concerned about is the following: If your dog goes outside and accidentally steps in poop and you don't fully clean his paws and your baby crawls around on the floor and her hands touch some poop stain and she subsequently sucks her thumb, can she get e coli bacteria or virus? Our baby was just diagnosed with e coli bacteria and we are trying to figure out what caused it.