What is the Risk? - Household Germ Study

A newly released “study”, the 2013 NSF International Household Germ Study, has sparked some media attention. http://www.nsf.org/business/newsroom/pdf/2013_germ_study_FOR-WEB-ONLY.pdf

The summary report discusses the analysis of 14 common kitchen items for the presence of E. coli, Salmonella, yeast and mold, and Listeria. In they identify:

The six “germiest” items contained the following microorganisms that can cause sickness:
1.) Refrigerator vegetable compartment: Salmonella, Listeria, yeast and mold
2.) Refrigerator meat compartment: Salmonella, E.coli, yeast and mold
3.) Blender gasket: Salmonella, E.coli, yeast and mold
4.) Can opener: Salmonella, E.coli, yeast and mold
5.) Rubber spatula: E. coli, yeast and mold
6.) Food storage container with rubber seal: Salmonella, yeast and mold 

And share their analysis on organisms found.

• E. coli – 36 percent of items contained E. coli. Items with E. coli included the refrigerator meat compartment, rubber spatula, blender gasket, can opener and pizza cutter.
• Salmonella – 36 percent of items had Salmonella including the refrigerator vegetable and meat compartments, can opener, blender gasket and the rubber seal on a food storage container.
• Yeast and mold – All 14 items (100 percent) tested positive for yeast and mold, and six items (43 percent) tested positive at concerning levels. The six items with concerning levels of yeast and mold were the refrigerator vegetable compartment, rubber spatula, blender gasket, refrigerator ice and water dispensers, and the rubber seal on a food storage container.
• Listeria – 14 percent of items tested positive for Listeria. The refrigerator vegetable compartment contained Listeria, as did the refrigerator door seal.

While the summary of the “study” highlights the need for cleaning in the kitchen, it is unknown to what degree this is actually a scientifically based study (statistically sound, peer reviewed, etc). The results are also questionable - the percent of samples found to be positive for Salmonella and E. coli is very high compared to previously published studies. (It is also important to note that this is generic E. coli, not necessarily pathogen E. coli). It would have been nice if they published the actual results so we could see the number of kitchens sampled (was it one kitchen?), percent positive for each item, etc.

Another item missed in this report is the impact of cross contamination during handling of raw foods and subsequent cleaning. This is when there is most likely to be transfer of pathogens to food contact surfaces, including appliance, as well as other foods. Along with this, there is the need for cleaning practices immediately after handling and processing (proper use of cleaning cloths and the use of cleaning/sanitizing agents). 

So yes, proper, routine cleaning of kitchen appliances and utensils is very important, and NSP does provide nice links for cleaning various kitchen appliances, but they miss what many consider a bigger risk for pathogen cross contamination in the kitchen – the potential for cross contamination during handling, processing, and subsequent cleaning. And there will be many who read this and overreact, thinking that their kitchen is full of Salmonella. Unfortunately, too others will carry this story not making any qualifying comments, but rather will probably further embellish upon the results.