2009 Potential for Bacterial Growth in the Refrigerators of College Students

There are many areas of the kitchen that can harbor bacteria. More cases of bacteria related food borne illness occur in the home than any other location. Young college aged adults often overlook areas of the kitchen that should be cleaned on a regular basis.

Purpose: To assess the presence of microbes in apartment refrigerators and compare UV-C light and Clorox wipes as disinfecting agents.

Methods: Bacterial samples were taken from ten student apartments, five of which had female residents and the other five had males. Subjects had no previous knowledge of what date, time of day, or from which area of the kitchen the samples would be taken. Each refrigerator was swabbed using 3M Quick Swabs^TM for presence of bacteria. The middle shelf of each refrigerator was swabbed initially, and then split into two halves. One halve was treated with Clorox Disinfecting Wipes and then swabbed again following a two-minute drying period. The other halve was treated with UV-C light 2 inches above the surface for 30 seconds (3X the manufacturer directions) and then swabbed again.  Media from swabs were poured on 3M Petrifilm^TM Aerobic Count Plates and incubated at 37 ̊F for 48 hours. Following the incubation period, samples were photographed and assessed for bacterial growth.

Results: Of the four refrigerators initially tested, all Petrifilm^TM plates had a high concentration of microbial growth spots that ran together and were too numerous to count. In ½ of the samples the Clorox wipes eliminated all of the bacteria. The other ½ of the samples treated with wipes eliminated most of the bacteria leaving behind an average of 11 spots on the plate. The UV-C light was able to eliminate most of the bacteria, however was unable to completely eliminate all of the bacteria present in each of the samples.

Conclusion: Refrigerators in college apartments harbor bacteria that may be harmful to students. However, these bacteria can be eliminated upon regular cleaning with Clorox wipes. Although UV-C light is able to eliminate most of the bacteria present in a refrigerator, Clorox wipes are more.  Another benefit of Clorox wipes over UV-C wands is the difference in cost and availability.

Molly Bray and Jessica Agnew Hoeppner presenting at the Minnesota Dietetic Association annual Meeting May 7, 2009, St. Cloud, MN