Does the five second rule really work?

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.

研究人员发现沙门氏菌可以urvive 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.

Think a doughnut dropped on your sparkling kitchen floor might be edible with just a quick brush off? It might be -- if you'd have no problem eating something out of the garbage. A study from the Hygiene Council (sponsored by the company that makes Lysol) found that kitchen floor just in front of the sink has more bacteria (830 per square inch) than the trash can (411 per square inch). Other surprises included the fact that the sponge held 60 times more bacteria than the pet's food bowl and that the kitchen counter was more germy than the toilet seat [source:CBS News].

In fact, toilet seats get a bad rap all around. A recent study by Gerba has shown that they're not even the dirtiest place in the bathroom. That honor goes to the toilet paper dispenser, with more than 150 times the bacterial levels of the porcelain throne. The next most contaminated spot is the paper towel dispenser, which harbors 50 times more germs than seats [source:Reuters].

To further defend the commode, your cell phone carries 25,000 germs per square inch, while toilet seats hold only 344 bacteria in the same space -- and we all know how much time we spend with our mobiles pressed close to our mouths [source:Sinovic]. Among the germs clamoring to join our conversations are staph, found on nearly half of 25 random mobile phones tested by Gerba [source:ABC News Health].

When the "germ guru" turned his attention to another everyday item -- women's purses -- the results weren't any more encouraging. Through a small random field test, the numbers of bacteria found on the bottom of ladies' bags ranged from small numbers to the nation-sized amount of 6.7 million [source:Leamy].

Fortunately, most of the germs that are crawling around our desks, on our phones and beneath our bags are of the benign kind and are kept under control with basic hygiene. But people with compromised immune systems, or those who spend time in areas likely to be contaminated withE. colior salmonella, should definitely think for at least five seconds before putting anything in their mouths that has touched the floor.