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Re: RES: [compost_tea] Compost and E. coli
Let's go through different kinds of coliform bacteria. There are total coliform bacteria, fecal coliform bacteria, fecal E. coli, and then the real bad guy, E. coli O157.
When you think about these bacteria, you need to be aware that the surface of a vegetable is very different from milk, or steak or macaroni and cheese.
Milk and meat are sterile, or should be, when they are in the animal. Macaroni should be cooked, and thus have no harmful pathogens. These foods should not be contaminated with pathogenic microbes. But they are all excellent food resources for all kinds of microbes. If they become contaminated, microbes can grow rapidly and cause serious problems for people, unless the kind of microbe is carefully controlled, as in cheese, or yogurt.
But vegetables start life with all kinds of microbes, need to grow with all kinds of microbes on their surfaces, and humans are used to eating vegetables, wheat, corn, salad, fruits, etc with all kinds of microbes on them. You need these microbes to have a healthy digestive system.
So, there’s a huge difference if we talk milk or if we talk plants. Don't go ballistic about microbes on plant surfaces or on plant debris. They are supposed to be there.
Coliforms can be present in soil, in water, in compost, and are normal in these places. Coliforms are just a typical set of bacteria, most are not pathogenic, not a problem. If you have these on the surface of your vegetables, it's ok. We need to consume some of these critters.
Total coliform counts include the E. coli found in human digestive systems. You need E. coli in your digestive system for proper digestion. Many coliforms are found in other animal's digestive systems. If these coliforms are in your milk, you should worry because milk is high in sugars (lactose), and protein and the organisms grow very fast, use up oxygen very quickly, and cause the milk to sour, and smell very bad. You drink it, you are going to be sick. But if these microbes are on your vegetables, big deal. There isn’t enough sugar or protein on a vegetable surface to allow them to grow quickly. Again, a few of these guys at a time is perfectly ok.
Fecal E. coli - these are the specific kinds of coliforms that indicate there is a possibility that human pathogens (microbes that cause typhus, cholera, food poisoning) COULD be present. You need to find the source of contamination and end it.
Do you need to go ballistic that you have some contamination? If it’s milk, yes, you need to deal with it NOW. But if it’s meat? Probably no reason to go ballistic. Or on your vegetables. The simple solution is to wash the surfaces of these materials. Cook your meat. And figure out why you have contamination and work to remove the source of contamination. You should do what is necessary to remove the source of contamination, prevent any further contamination. Alter the habitat so that E. coli cannot grow. But you have time to deal with the situation usually.
If the contamination was from someone sick with E. coli O157, or from an animal carrying this bacterium, then this human pathogen could be present. E. coli O157 doesn't just come from anywhere. There has to be a source of this bacterium. You must track that down NOW! Do not wait. Shut the operation down until you find the source of contamination. Change the operation once your find the source of contamination.
So, is testing necessary? Yes. But how often? Every steak? No. Each bottle of milk? No. Every windrow of compost? No. You need to establish a history of no-problems, and then sample every so-often depending on production.
If fecal E. coli are found, then testing should be more frequent until you can be assured that the source of contamination was removed.
The problem is much more serious in a dairy, or slaughter house. There are all kinds of other organisms in plant material, and the aerobic habitat is not conducive to E. coli winning out over all those other organisms.
In a dairy, you have to find out who isn't paying attention to cleanliness. In a compost situation you have to figure out where uncomposted material is getting mixed with composted material in significant enough amounts that the new material is able to overwhelm the composted material.
If you have a healthy pile of compost, with all the good aerobic organisms in the compost, how long does it take to chew up the E. coli in the contaminant?
Let manure with high numbers of E. coli, and good numbers of beneficial organisms, sit in a pile for a few months, and the E. coli disappears. All on “it’s own”. No, not really all on it’s own. The beneficial aerobic organisms out-compete it, keep it from getting any food, consume it, etc, and so no E. coli.
With a good food web in the manure, E. coli disappears within three months in the testing we have done. With not-so-good a food web, E. coli took longer to disappear. If the pile is anaerobic, the E. coli are still there.
If you contaminate a pile of good compost, how long does it take for the E. coli to disappear? If the food web is active, complete, high numbers of aerobic organisms, even a billion E. coli added to the pile will be gone within 24 hours. If the "compost" is anaerobic, and the food web isn't present, E. coli added to the pile in high numbers will be detectable for months and months.
You need to be aware of the kind of coliform people are talking about. If someone says coliform, ask if it's a coliform of concern. If the test was positive for fecal coliforms, as long as it is plant matter, so what? If the test was positive for fecal E. coli, figure out where the source of contaminaiton is from. If it is positive for E. coli O157, go ballistic.
Go ballistic when you need to, but the rest of the time, be sane about these problems. There is no need to succumb to paranoia or fear. Healthy respect for microbes, yes, but we can keep them in control by managing their habitat.
Elaine Ingham
President, Soil Foodweb Inc.
Corvallis, OR
Port Jefferson, NY
Lismore, NSW, Australia
Hilversum, The Netherlands
www.soilfoodweb.com
President, Soil Foodweb Inc.
Corvallis, OR
Port Jefferson, NY
Lismore, NSW, Australia
Hilversum, The Netherlands
www.soilfoodweb.com
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