Q: I have seen so many headlines saying that vegetables are contaminated with E. coli bacteria. I grow a lot of my own vegetables, and I am wondering how this happens and how to prevent it. Why do commercial farms that have so many ways to protect their product seem to be the worst at this?
A: I am not sure you are right in your premise that big farms have more problems than small farms or people growing produce in their backyard. The big guys will have the recalls that get a lot of attention, but a local farmers market vegetable seller won’t even get a recall. A problem with the food from a backyard garden will probably get blamed on something else and not E. coli on the vegetables.
So, where does the E. coli bacteria come from in the first place? It is found in the lower intestine of most warm-blooded animals. It is mostly beneficial, as it helps prevent bad bacteria from growing. It is expelled with fecal matter. In the intestine, it is growing mostly without oxygen. Outside the body, in fresh air, it grows and multiplies rapidly for a few days.
There are a variety of different strains of E. coli bacteria. A few cause serious food poisoning, septic shock, meningitis, urinary tract infections, and diarrhea. Diarrhea from E. coli kills hundreds of thousands of children each year.
How does E. coli get on the vegetables? Any water source that is contaminated with animal waste spreads E. coli. This can be as simple as rainwater splashing cat, dog, raccoon, or other animal waste onto the vegetables. How are animal waste products handled when removed from your garden? By a gloved hand or with a shovel? If the tools or gloves are not sterilized, they can spread the bacteria. A person who doesn’t wash their hands after going to the bathroom and before harvesting vegetables can also spread E. coli.
Any floodwaters that run through a garden should be considered contaminated and the vegetables not edible unless very thoroughly washed.
Uncomposted manure is filled with E. coli. It should sit for months before being used. If it is to be composted, extension recommendations are for the compost to reach an internal temperature of 130 to 140 degrees F for at least five days in two separate composting cycles. The compost pile should not be near the garden.
As for the larger growers, it doesn’t take very long for a single contaminated person or tractor to contaminate dozens of boxes of produce.
All vegetables, even ones growing in your own yard, should be washed before eating. There are special vegetable soaps you can buy, but I don’t know anything about them.
Some vegetables, such as lettuce, are easy to grow hydroponically. No soil, no problems, right? Not so fast. The water used in the hydroponic system must be carefully maintained so that it doesn’t become contaminated with E. coli or other bacteria.
Sanitation is a key component of vegetable gardening but is often taken for granted. Leafy vegetables, such as kale, lettuce, and spinach, have lots of surfaces for E. coli to attach to and should be washed extra carefully.
