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Bacteria Bags: Backpacks, Purses, and Reusable Grocery Bags

Dear Dr. Dave and Dr. Dee,

My daughter carries a small backpack for a purse and leaves it on the floor of the fast food restaurant while eating. Isn't that not safe as far as someone could steal it from underneath the table? Shouldn't she sling it onto the back of the chair? I have told her these things, but she ignores me.


Bag Battle

Dear Bag battle,

It is possible for a bag or wallet to be stolen when a backpack or purse is left out of sight under the table or back of the chair. The best place for a small backpack or purse while dining is on the lap, with the napkin over it.


Another reason to not leave purses or backpacks on the floor is health concerns.

Microbiologist Amy Karen studied women's purses and found the bottom of purses had harmful bacteria such as salmonella, E. coli, and herpes. 7News ( swabbed seven backpacks and found all covered in bacteria, and all but one has staph bacteria, which could cause skin infections (McNally, K., "Would you like herpes with that handbag madam?" MSN UK Life & Style, Nov 19, 2009; "Special Report: Toting Trouble," 7News,, 2/12/07).

Microbiologist Dr. Charles Gerba tested handbags for ABC News and discovered "every single one had at least some bacteria, most had tens of thousands and a few were saturated with millions. One even had 6.7 million bacteria. Half of the bags tested positive for coliform bacteria, which indicated the possible presence of human or animal waste" (Leamy, E., "Your Purse Could Be Making You Sick,", Good Morning America, August 8, 2006).

In research on reusable grocery bags, Williams & Gerba, et. al. found that all reusable bags randomly selected for the study had large numbers of bacteria, half had coliform bacteria, and 8% E. coli. Bacteria also increased 10-fold when reusable bags were stored in the trunk with meat juices for two hours (Williams, D.L., Gerba, C.P., Maxwell, S., Sinclair, R.G., "Assessment of the Potential for Cross-contamination of Food Products by Reusable Shopping Bags," Biblographic citation: Food Protection Trends, vol. 31, no. 8, pp. 508-513, August 2011 Volume 31, Issue 8).


1. Keep Off floor: Avoid putting purses or backpacks on the floor and always hang it on a hook, especially in public restrooms.

2. Avoid Cross-Contamination: Keep purses and backpacks off the kitchen table or counters where food is prepped or eaten as bacteria will transfer to those areas from the bags.

3. Beware of Shopping Carts: Do not put purses or backpacks in shopping carts. Dr. Charles Gerba examined shopping carts from five different cities across the United States and found 72% of shopping cart handles were contaminated with fecal bacteria: coliform or E. coli (Gerba, C. & Maxwell, S., "Bacterial Contamination of Shopping Carts and Approaches to Control," Dept. of Soil, Water and Environmental Science, University of Arizona, 2007).

4. Machine Wash: Fabric purses, backpacks, and reusable grocery bags. Unless reusable shopping bags are regularly washed, they will turn into bacterial swamps, according to Dr. Gerba, and "It's like wearing the same underwear every day" (Carroll, L., "E. coli found on 50 percent of shopping carts,", 3/1/11).

5. Wipe Down purses made of leather or vinyl with soap and water or disinfectant.