Re: [compost_tea] MICROBIOLOGY TESTING of COMPOST TEAS

From: <soilfoodweb_at_aol.com>
Date: Wed, 22 Dec 2004 10:48:37 -0500
On this list serve, we've been pointed to the Woods End website before, and we've had this discussion before at least once, maybe twice. 

First off, Woods End uses plate counts, and I always laugh when they describe the plate count approach they use as determining active organisms. 

Any microbiologist worth their degree would tell you that plate counts cannot and will not give information about active organisms.  Plate methods tell you about spores, about dormant stages mainly.  Less than 0.01% of the total population of bacteria, or fungi, depending on which medium you are using in the plate, can actually grow on any plate. 

So, what usefulness does the plate count method have for telling you what you need to know with tea? 

Plate count methods are useful for determining the numbers of dormant and active numbers of something that we know how to grow in lab conditions.  So, E. coli, for example.  Plate counts can assess E. coli just fine, because we know the conditions that E. coli needs to grow in the lab.  Lots of sugar, some antibiotic to kill other bacteria, and a lid on the plate so oxygen will be used up and become slightly limited during the growth cycle.  There are labs all over the world that do this assessment.  Pick the one closest to you to do this assay.

More interesting to me, and which I have discussed before, is the information on the Woods End website summarizing the Compost Tea Task Force position on E. coli.  Several points are  somewhat twisted in their summary, and since people are showing an interest in this website again, I'd like to summarize again.

Here's the section on E. coli, for example: 

"The Task Force recommended that teas be tested for E. coli IF," (and please get this part, that's an IF)

"1.  They contain nutrient additives such as molasses,"
(this is not quite right, only molasses is singled out in the Task Force recommendations.  But the reason for this kind of rule is the tea going anaerobic during brewing, and setting the stage for conditions being right for E. coli to grow.  This could happen with any additive, with immature compost as well, so there was lots of discussion about this.  The recommendations singled out molasses, but it is more correct to discuss any additive, including the compost.  The reason for this concern should be focused on, not just outlawing certain materials,  Additives can be used, if oxygen is assessed THROUGH the whole brew cycle, not at just a couple points during brewing.  Brinton's article about aeration in brewing misses this point, so again, I chuckle alot. 

"2.  are to be used more than 1 hour after their production"
  (The CTTF report talked about compost EXTRACTS that are more than 1 hour post-production, not compost tea.  and not in the recommendations, just in the report.  The real problem is that production wasn't defined, so I objected to this idea being in the report.  Since one could define the production period to be anything wanted, this part was ambiguous at best. Anyone selling tea to another person would have to test the tea for E. coli, if this were actually under consideration)

"3.  are to be used on crops that are to be eaten directly (grains would be exempt) and will be harvested less than 90 days after application of tea."
 
"Two batches of the tea should be tested and the average MPN or CFU of E. coli per 100 ml of tea should be less than 127."

Hum, again, not quite what was in the recommendations, although close.  The recommendations said that replicated testing would be required.  That wasn't defined in the recommendations, and so I objected to the lack of clarity there.  By default, replication would be two tests.  Which is not scientifically valid, so, the point of only two tests would be....what?  Why two?  Why not just one?  If you are going to bother with two, then why not three, so at least valid replication is performed?

Nor was it clear in the recommendations whether the replicated testing applied to each batch of tea, or to the brewer one was using.  Again, I objected that these things were not made clear. 

The recommendations also stated that if the compost was made according to Organic regs, or if the compost was tested for E. coli, then the tea did not have to be tested. 

Why did that get left out of this summary? 

The Woods End website also presumed to put a number on the E. coli level.  There was no E. coli level given in the recommendations.  Different states have different regulatory levels, and therefore that value could be different in different states.  What is magical about 127 CFU. or MPN, of E. coli per 100 ml?  That works out to be 1.3 CFU per ml.  There's some clear testing that shows if E. coli hits a leaf surface in a normal condition that it will be gone in 24 hours.  So, why this level, and not another? 

We need more testing in compost tea situations, and hopefully the USDA will designate more money to testing.  

Which was the point, I believe, of several people with vested interest in getting money to do testing being on the Compost Tea Task Force.  They are concerned with money moving into their programs or companies, and so hype the concern over human pathogens.  They use scare tactics to frighten people into doing un-necessary testing.  

Anyway, the recommendations from the Task Force have been approved by the NOSB, and are before the NOP for consideration.  For those making compost according to organic regs, and using their own compost tea, whether areated or not, with additives or not, there isn't much need to worry.

Those selling compost tea to others need to document that the tea is E. coli free.  I prefer flat-out no detectable E. coli in the material and stop fussing about whether the limit would be 1.3, or 8.0, or something higher.  If something goes haywire in the tea production, if the compost had no-detectable E. coli, then you don't have to worry.  If you are getting compost with E. coli in it, then you need to ask; what's going wrong in the compost production. 

Joe Richards, Ross Orner, Leon Hussey, Tim Felegy, and others (see the SFI website, or call and talk with Brian) for example, continually produce worm compost, thermal compost, and humus with no detectable E. coli, high levels of
fungi, great protozoa, and decent beneficial nematodes in their materials. 

The easiest way to deal with all this is to have tested compost.  Or put tea that you might not know about E. coli on your non-food crops.  The work that Steve Ingham at Univ. Wisconsin is doing on how long do E. coli survive on leaf surfaces in normal field conditions is really interesting.  24 hours is the norm. 

Can we set-up lab conditions that result in E. coli surviving on leaf surfaces?  Sure.  And that might be useful info to have, so that if weather is wierd, then you'd know to wash your food before eating it. 

But getting bent out of shape about "E. coli is everywhere, and we're all going to die" is silly.  Taking extra care when you are sick, absolutely.  Making sure restaurants maintain high levels of sanitation?  Absolutely. 

Its probably sanitation that has lengthened the human life span, because we prevent disease.  We alter the habitat so diseases are not with us.  Proper sewage treatment is a must, and  that is the biggest factor in increasing human life span.  Sure, antibiotics have contributed, hospitals with immediate care facilities reduce fatalities, but the biggest single factor in lengthening human life span has been  sanitation. 

But let's be reasonable about it.  We all contact, and probably consume, E. coli everyday.  In small numbers, not a problem, unless you are already sick.  Care is required.
--
Elaine Ingham
President, Soil Foodweb Inc.
SFI Corvallis, OR
SFI Port Jefferson, NY
SFI Lismore, NSW, Australia
SFI Cambridge, New Zealand
SFI Culiacan, Mexico
SFI Jerome, Idaho
SFI South Africa
http://www.soilfoodweb.com


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Received on Wed Dec 22 2004 - 11:25:31 EST

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