http://www.foxnews.com/lifestyle/2013/0 ... -cart.html
A study of 85 random shopping carts conducted by Dr. Charles P. Gerba found that 50 percent carried E. coli, while 72 percent contained coliform bacteria. "The exceptionally high level of coliform bacteria suggests that fecal material may be involved in cart contamination," the report further stated.
Duberg cites Gerba's findings for the answer: "[There are] 138,00 total bacteria per square inch of a shopping cart — an amount which exceeds the number of bacteria in the average public restroom," she says. "These are fecal bacteria capable of causing illness."