Manchester Metropolitan University study looked at five test foods left on the floor for intervals of three, five and 10 seconds. The bread with jam, cooked pasta, a slice of ham, a plain cookie, and dried fruit were deemed safe. The ham (high salt) and sugary bread and jam were both considered safe, with little sign of bacterial growth, when retrieved after three seconds on the ground. But the cooked pasta and fruit, however, both tested positive for klebsiella, a bacteria known to cause a range of diseases and infections, as well as soft-tissue conditions.”]
Source: https://gizmodo.com/how-to-safely-eat-fallen-food-with-the-5-second-rule-5910280