A study of 85 shopping trolley handles in parking lots of grocery stores, tested in 5 metropolitan areas across the US identified Escherichia coli on 18 trolleys (carts).
Since it is known that contamination of raw meat products with bacterial enteric pathogens, such as Salmonella, Campylobacter and E. coli, occurs on a regular basis, it suggests that exposure to enteric pathogens via shopping trolley handles occurs on a regular basis.
The authors assessed that total bacterial levels on shopping trolley handles were greater than those found in public restrooms and other public places and objects that are commonly touched in these environments (airports, bus stations, public bathroom, shopping malls, etc.), and concluded that supermarkets should consider offering complimentary sanitizing wipes for shoppers.
The full report can be found in Food Protection Trends, 2012:32,27-29.