Study Reveals High Bacteria Levels on Footwear

CIRI Staff

A study which investigated germs collected on footwear, by Dr. Charles Gerba, microbiologist and professor at the University of Arizona, and The Rockport® Company, found large numbers of bacteria both on the bottom and inside of shoes; averaging 421,000 units of bacteria on the outside of the shoe and 2,887 on the inside. Some of the bacteria found on the shoes included: Escherichia coli, known to cause intestinal and urinary tract infections, meningitis and diarrheal disease; Klebsiella pneumonia, a common source for wound and bloodstream infections as well as pneumonia; and Serratia ficaria, a rare cause of infections in the respiratory tract and wounds.


Snapshot: Footwear Study Results
  • Coliforms were detected outside of the shoes on 96% of the shoes. E. coli was detected on 7 of the shoe bottoms (27%). No coliforms were detected on the inside of the shoe.
  • Transfer of bacteria from the shoes to uncontaminated tiles ranged from 90% to 99%.
  • The average number of bacteria on Rockport shoes before washing and after washing is showing a 99% reduction in the numbers of bacteria on the outside of the shoe and a 90% reduction of bacteria on the inside of the shoe after washing.
  • Specifically there was a 99% reduction of the bacteria coliform on the outside of the shoes after washing.

The goal of the study was to verify bacteria levels on footwear and the effectiveness of machine washable shoes in reducing those levels inside and outside the shoe surface. The project also investigated the role of shoes in the movement of bacteria from contaminated floor spaces to other surfaces.

"The common occurrence (96 percent) of coliform and E. coli bacteria on the outside of the shoes indicates frequent contact with fecal material, which most likely originates from floors in public restrooms or contact with animal fecal material outdoors," said Gerba. "Our study also indicated that bacteria can be tracked by shoes over a long distance into your home or personal space after the shoes were contaminated with bacteria."

Simply washing the shoes with detergent was found to eliminate the fecal bacteria and reduce all bacteria by 90 percent or more.

"Life of a Shoe" Online Video

To illustrate the prevalence of germs and bacteria on footwear Rockport launched, a micro site featuring a video short that follows a pair of feet (or shoes) navigating through an average city day. The video demonstrates how vulnerable shoes are to bacteria and exactly how we track it to other locations.
Footwear Study Methodology

New shoes were worn for two weeks by 10 study participants. Following the wear trial period, the bottom and inside of the shoes were sampled for total number of bacteria and coliform/E. coli. Scientists washed the footwear in a standard washing machine using conditions suggested by the manufacturer: cold water, 12 minute wash cycle using detergent, air dry for 24 hours. Wash water temperature was 24 degrees C.


Study Reveals High Bacteria Levels on Footwear:  Created on May 3rd, 2008.  Last Modified on May 3rd, 2008


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