O157:H7

What is O157:H7 ?

This is the strain of Escherichia coli that causes the most problems when consumed. It is also one of the strains that has been continuously found in bagged spinach leaves. 

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In 2012, there was an outbreak of E. coli across five states, including Virginia. The outbreak investigation indicated a Wegmans brand of spinach, produced in Massachusetts, was one possible source of the outbreak (Source). This is not the first time a type of spinach has been recalled due to an E. coli outbreak. 

In 2007 the FDA finalized a report on a spinach outbreak from the previous year. By using DNA tracing they were able to determine that the source of the E. coli was from wild pigs that may have been near where the farming. There were also traces of cattle or human fecal contamination in surface waterways. There was no conclusion as to how the spinach actually became contaminated but the investigation was able to narrow it down to a few possibilities (Source).  

Why is this a continuous problem with spinach ?

Last week in microbiology, our class did several experimental tests to find out the best way to clean spinach leaves. The samples were from one bag of spinach labeled “pre-washed.” Our control group was an unwashed leaf from this bag. What we found was actually shocking to me. No wonder there have been several recalls on bagged spinach. The leaves all had E. coli bacteria on them, despite the fact that these had already been "washed". I have always been told to make sure I wash everything from the grocery store before using, but now I understand why.

Just in case you were wondering, the “Fit Spray” was the most effective way to clean spinach. I have used this spray before on apples and think it leaves a gross citrus taste, so I personally would not want to use it. It just makes me a little curious as to what is considered "washing"and when does this happen throughout the growing to packaging process.


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