Battling Food-Borne Bacteria

The FDA has long advocated that we wash fresh vegetables and fruits to rid them of disease-causing bacteria. Unfortunately, new research indicates that simple washing may not be enough.

IDEXX Labs, a diagnostic testing service, examined 39 samples of fresh bean sprouts purchased from grocers, and found that each gram of sprouts averaged over 10 million coliform bacteria. These bacteria do not pose a disease risk themselves, but their presence suggests the potential for contamination by other soil-dwelling pathogens. Ten of the samples were contaminated with E. coli. Similar bacterial findings have been noted in studies of other vegetables.

In one experiment, researchers purposely contaminated sprouts with E. coli or Salmonella to determine if washing would remove the pathogens. After three washings in clean water, significant numbers of microbes remained—many thousands of times the number needed to cause disease in those with weakened immune systems.

In addition to surface bacterial contamination, pathogens can make their way inside plant cells. Japanese researchers found that radish plants grown from seeds soaked in E. coli-contaminated water harbored bacteria within their cells.

Fresh manure and human feces are common crop fertilizers in many parts of the world, and the U.S. is now importing a great deal of food from other countries. The FDA cannot be relied upon to keep contaminated food out of the food supply, since the agency has the resources to inspect fewer than 2% of non-meat imports.

Scientists are currently working on various chemical washes to kill surface bacteria. One mixture that has proven effective is a combination of vinegar and hydrogen peroxide.  Based on information in: Science News, 30 May 1998; New Scientist, 21 March 1998