Mad rantings about politics, evolution, and microbiology. Comment policy: say what you want, but back it up with an email address. I don't like anonymous trolls.
You can't go wrong with the title "Residence time and food contact time effects on transfer of Salmonella
Typhimurium from tile, wood and carpet: testing the five-second rule." And it only gets better.
Here's the abstract:
Aims Three experiments were conducted to determine the survival and transfer of Salmonella Typhimurium from wood, tile or carpet to bologna (sausage) and bread.Methods and Results: Experiment 1. After 28 days, 1·5 to 2·5 log10 CFU cm-2 remained on tile from and the more concentrated media facilitated the survival of S. Typhimurium compared with the more dilute solutions. Experiments 2 and 3. The bacterial transfer rate to food decreased as the bacterial residence time on the surface increased from 2, 4, 8 to 24 h with transfers of 6·5, 4·8, 4·6 and 3·9 log CFU ml-1 in the rinse solutions, respectively. Over 99% of bacterial cells were transferred from the tile to the bologna after 5 s of bologna exposure to tile. Transfer from carpet to bologna was very low (<0·5%) when compared with the transfer from wood and tile (5-68%).
Conclusions: (i) Salmonella Typhimurium can survive for up to 4 weeks on dry surfaces in high-enough populations to be transferred to foods and (ii) S. Typhimurium can be transferred to the foods tested almost immediately on contact.
Significance and Impact of the Study: This study demonstrated the ability of bacteria to survive and cross-contaminate other foods even after long periods of time on dry surfaces, thus reinforcing the importance of sanitation on food contact to minimize the risk of foodborne illness.
And you have to love this formula:
It's a great paper.
Comments
Those guys got scooped! The 5 second rule even won the IgNobel in 2004:
http://www-tech.mit.edu/V124/N41/41_ignobels.41n.html
Posted by: apalazzo | April 3, 2007 7:30 PM
Also featured on Mythbusters episode 39 (aired 19 October 2005).
http://en.wikipedia.org/wiki/MythBusters_(season_3)#Five-second_Rule
Posted by: Ex-drone | April 3, 2007 8:48 PM
I saw it at the AAAS meeting in Washington in 2005. I think Jillian Clarke's award was presented by the guy in the cowboy hat from Nashville (Gundlach) who proved the connection between country music and suicide.
BUT she didn't test carpet. Her answer cracked up the house. It was, "We didn't have funds sufficient for testing the hypothesis on carpet. And besides, that's just gross!"
So Dawson et al have a claim to broadening the field.
Posted by: Bob Calder | April 3, 2007 9:59 PM
well, not to make a pun or running gag or anything, but did they think about trying it with peanut butter?
Posted by: skippy | April 7, 2007 1:09 PM
I still don't think these experiments are testing the five-second rule. Based on the abstract, it sounds like the linked article is testing how long bacteria survive on different surfaces, not how quickly it transfers to food.
The Mythbusters episode only compared 2-second exposure to 5-second exposure. Then they let the food incubate bacteria for several days.
To me the relevant question is this: if you drop something on the floor and pick it up right away, is it safe to eat right then, compared to eating something that's been sitting on the floor a long time.
The ideal experiment would compare 5-second exposure to 5-minute, 1-hour, 5-hour, and 1-day exposure. I'm still not sure that's ever been done.
Posted by: Dave Munger | April 9, 2007 8:52 AM