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Sprouting a Food-Borne Infection

© Neal Rolfe Chamberlain

One problem with being a Microbiologist is that nearly everything you eat can be a potential source of an infection. Eating raw oysters can give you hepatitis. Eating partially cooked hamburgers can result in an Escherichia coli O157:H7 infections. Eating raw pork can result in trichinosis. Even fresh fruits and vegetables can contain microbes that result in one illness or another.

Now don't get me wrong, this hasn't stopped me from eating. My wife can attest to my larger than average girth. Now a new source of food-borne illness is sprouting out to get me. Actually it is not new. Cases of diarrhea resulting from consumption of alfalfa sprouts have been reported since 1973. Seven different well-documented outbreaks of diarrhea have been reported in just the last two years (1997 and 1998). Now even my sprout laden salads are suspect.

A recent article from the journal, Emerging Infectious Diseases, contained some very interesting reading about contaminated seed sprouts and how they have become sources of food-borne illness. This article mentions that alfalfa seeds are harvested from alfalfa plants. Alfalfa is a common cattle feed that is often fertilized with manure. The seeds can be contaminated in the fields after fertilizing the alfalfa plants. Interestingly only a few hundred diarrhea-causing bacteria are on a gram of seeds when planted. During the germination and growth periods up to 10,000,000 diarrhea causing bacteria can be present per gram of mature sprout without causing any noticable damage to the sprouts.

Several different disease-causing bacteria have been obtained from these contaminated sprouts [Salmonella species (diarrhea), Bacillus cereus (diarrhea/vomiting), and Escherichia coli O157:H7 (diarrhea and kidney damage)]. These bacteria can cause serious infections in the elderly, young children, and in the immunocompromised. To prevent these infections researchers have found that soaking alfalfa seeds in 20,000 ppm active chlorine for at least 10 minutes before sprouting will kill most of the bacteria on the seeds without destroying the seed's ability to germinate. This is not a perfect solution. The authors of the Emerging Infectious Diseases article state a large number of measures are needed to properly prevent outbreaks of illness due to contaminated seed sprouts.

The bottom line is that most sprouts on your average salad bar won't result in a food-borne illness. However, if you are elderly, very young, or immunocompromised it might be best to stay away from those sprouts. Eventually, I forsee better controls to prevent contamination of this food product but don't take my word for it go to the article yourself (Emerging Infectious Diseases).

Take Care and Think Microbiologically!