Does the five second rule really work?

Salmonella and the Five Second Rule

In May 2007, scientists at Clemson University in South Carolina decided to find out just how much ick sticks to food as well as to various floor surfaces. By applying a "salmonella soup" to tile, wood and nylon carpet, the researchers were able to not only see how long the germs lived in those environments, but also how many of the micromenaces transferred to slices of bread and bologna.

The researchers discovered that salmonella could survive on all three surfaces for up to four weeks -- and that they thrived particularly well on the carpet. As for how quickly the germs climbed aboard the bologna and bread, it was found that the longer the contact with the floor, no matter what the surface, the higher the transfer of germs. So, when left on the floor for just five seconds, both foods picked up between 150 and 8,000 bacteria. But if they were left for a full minute, the rate was magnified 10 times [source: McGee]. Combine this with the fact that it can take just 10 of some strains of salmonella bacteria to cause infection, and it becomes clear that grounded food should stay that way.

But surely the pH of our saliva and stomach acids can wage a good fight against contaminated food, right? "No," says microbiologist Charles Gerba, the "germ guru" of the University of Arizona. "Many viruses survive the low pH -- in fact, they like it. Viruses like hepatitis A and norovirus survive well at low pH. So do bacteria like salmonella. Any bacteria that infects the intestine can survive the low pH long enough to get to the intestine."

It's also important to consider where your Twinkie or hot dog has landed. According to Gerba, there is quite a difference between floor germs based on their location. He says that public restrooms top the list. He also adds, however, that all floors and carpets are dangerous "because people track bacteria and viruses on their shoes all the time. About 93 percent of the shoes we have tested have fecal bacteria on the bottom."

Unfortunately, public floors aren't the only germ fields we should be concerned about. Read on to discover some other surprising bacterial havens.