Shop workers who handle food should not do so immediately after handling money and without washing their hands, according to researchers at the Center for Food Safety and Quality Enhancement and the Department of Food Science and Technology at the University of Georgia.

The scientists used pennies, nickels, dimes and quarters from general circulation to test whether the coins could transmit the potentially deadly bacteria E. coli 0157: H7 and Salmonella Enteritidis directly from hands to food.

Despite being cleaned with detergent, sterilised and air dried in controlled conditions, the coins were all still covered with bacteria. The scientists then left the samples within a room environment, with room temperature and 40% humidity, and discovered that E. coli 0157: H7 survived for 11 days on quarters. They also found that Salmonella Enteritidis was still present on the surfaces of dimes after nine days.

The researchers warned that as the bacteria lasts for so long, it is likely that the coins can contaminate other surfaces.