Ah, yes.  I have not reported the results in a long time from one of the (hundreds of) journals to which I’ve subscribed for more than 40 years.  Applied and Environmental Microbiology, a publication of the American Society for Microbiology.

But, to be honest, this article really ruined my day.  Maybe my year.  Oh, and I’m sharing it with you because misery loves company.  And, I’m pretty sure this could disabuse you of a long held notion.  (And, moms and dads- your goose is probably fully cooked, now.)

Dr. Donald Schaffner (Rutgers)  and his grad student, Robyn Miranda, published the results of their study just recently.  The title:  Longer Contact Times Increase Cross-Contamination of Enterobacter aerogenes from Surfaces to Food.  And, just what idea did they debunk?   The FIVE  (or THREE) SECOND RULE!!!!!

Yup.  Now, these scientists say letting our food fall on the floor, scooping it up, and then popping it in our mouths is a terrible idea.    Yes, I know we have not died from this- yet.

But, Dr. Schaffner and Robyn studied four different kinds of surfaces- carpet, wood, ceramic tile, and stainless steel- to see if the five second rule worked.  The foods they checked?  Watermelon, bread, bread and butter, and gummy bears.  And, they didn’t limit their tests for five seconds- but spanned the duration with times ranging from less than one second, 5, 30, to 300 seconds of contact.

Now, for the technical microbial data: They used Enterobacter aerogenes (a common microbe that is non-pathogenic, even though it is related to Salmonella) and two different microbial media to amplify growth- tryptic soy broth and peptone broth.

The surfaces (25 cm² ) were inoculated with 1 ml of the microbial solution and then left to dry for 5 hours before the “oops” test began.  (This provided about 10,000,000 colonies on the entire surface.)   Then, about 16 cm² of the food was dropped from 12.5 cm of height and left for the various timed test periods. The research involved 128 different scenarios, and each were repeated for 20 assays.   (The one variable they did not test?  Presssure.  It should be obvious to all that this would make the “oops” situation a whole lot worse!)

Not surprisingly, the gummy bears managed to skate without terrible contamination.  And, the watermelon managed to suck up the most microbes and pose significant potential problems.  (It is clear that the wetter the food, the easier the microbial transfer- and being wet also serves as a better medium for microbial growth.)

Carpet- with its uneven surfaces- managed to pose the smallest source of problems.  The stainless steel and ceramic tile served as the worst.  (If you’ve been reading my blog for a while, you’ve heard me warn that hospital bathrooms with their ceramic tiles were breeding grounds for microbes.  Which is why- finally- hospitals don’t want visitors to use patient’s bathrooms.)  The wood surface  provided uneven results, as you saw in the above diagrams.

Basically, moisture, surface type, and contact time all interact to afford microbial contamination on the dropped food(s).  And, given the right surface and moisture contact, even 1 second of contact could do us in.

What a bummer!

NOT!

Because when something drops on the floor, we pick it up and immediately pop it in our mouths.  We are not giving those microbial contaminants a day to grow and multiply.  We give the little buggers a few seconds at best.

So, if we are healthy, this practice is still probably OK.  Probably not in cholera rich regions.  Probably not if we are already sick or run down.

But, if our food hits the floor, has no applied pressure, and it’s in our mouths within 5 seconds, we are probably ok.

Maybe, that’s why I was taught it was a 3 second rule.   Because that left me 2 seconds to pop it in my mouth!