But how much bacteria actually transfer in five seconds?
In 2007, my lab at Clemson University published a study -- the only peer-reviewed journal paper on this topic -- in the Journal of Applied Microbiology. We wanted to know if the length of time food is in contact with a contaminated surface affected the rate of transfer of bacteria to the food.
To find out, we inoculated squares of tile, carpet, or wood with salmonella. Five minutes after that, we placed either bologna or bread on the surface for five, 30, or 60 seconds, and then measured the amount of bacteria transferred to the food. We repeated this exact protocol after the bacteria had been on the surface for two, four, eight, and 24 hours.
We found that the amount of bacteria transferred to either kind of food didn't depend much on how long the food was in contact with the contaminated surface -- whether for a few seconds or for a whole minute. The overall amount of bacteria on the surface mattered more, and this decreased over time after the initial inoculation. It looks like what's at issue is less how long your food languishes on the floor and much more how infested with bacteria that patch of floor happens to be.