Scientists from the Clemson University in the US have gone some way to prove the validity of the five second rule (the rule whereby, if you drop some food, you have five seconds to pick it up before it’s considered too contaminated to eat).
Slices of bologna and bread left for five seconds took up between 150 to 8,000 bacteria from surfaces that had been contaminated eight hours earlier. However, left for a full minute, the food slices collected about 10 times more bacteria from the tile and carpet, and a lower number from the wood surface.
Granted, dropping your food in salmonella is generally speaking a pretty dumb thing to do, but dropping food onto a relatively clean surface and picking it up quickly is far better than leaving it for a while.