[USCC] O157 E Coli

[frank]

Tim Evans wrote

>I don't think the question of E. coli or fecal coliforms is really too
>significant, one is just a sub-set of the other and [so microbiologists tell
>me] the numbers aren't very different.  If there's no fecal content in the
>source material there won't be much of either.  It does appear that there is
>a small population in soil from wildlife, etc. - that's where 1000 fecal
>coliform per gDS for Class-A came from - it's roughly the ambient
>concentration.
>
>  
>
Tim,
 I hope your right that FC and EC are closely  the same in yard waste 
compost. I was trying to find some data without luck. That would mean a 
procedure where once time, mixing and temperature was met a sample could 
be sent into a local water lab for quantitray EC test and results 
returned in a day or two. If it failed composting could continue. If 
passed the compost could be moved to the 'clean' section of the pad, 
composting continued until stabilized or worms introduced. . It would be 
easy to do more testing and, I think, less chance of contamination from 
a failed windrow. I'm sure in Florida I will find the errors in my 
thinking : )  

Thanks
Frank

>However, I do absolutely agree with you that we need to be concerned about
>phytopathogens and propagules of pernicious weeds as well.  So for Quality
>Assurance purposes I would still recommend working on hitting
>time-temperature.  Part of the HACCP would be to consider what is in the
>feedstock and what is the intended use of the compost.  End-of-process
>testing can be used as a means of control [batch release protocol] but it is
>much better to have a Critical Control Point and to monitor it continuously
>to check that it stays within the Critical Limits.  End-of-process testing
>is then verification that the CLs are right and that there is no by-pass.
>
>I also agree that proficiency testing schemes for laboratories are valuable,
>and furthermore that they need to be blind tests, i.e. the lab should not
>know when the test sample is coming or that it is a test sample when it does
>arrive.  Proficiency schemes measure the competence of the labs and also the
>reproducibility of the methods. It is easy to be deluded by seeing numbers
>that they are different when in reality they might be the same within the
>limits of precision of sampling and analysis.
>
>regards
>
>Tim
>
>
>Dr Tim Evans
>TIM EVANS ENVIRONMENT
>Stonecroft, Park Lane, Ashtead, Surrey KT21 1EU England
>tel/fax +44 (0) 1372 272 172 mobile +44 (0) 7816 833 991
>tim at timevansenvironment.com
>
>
>-----Original Message-----
>From: frank [mailto:frank at compostlab.com] 
>Sent: 18 December 2006 22:44
>To: US Composting Council Compost Discussion List
>Subject: Re: [USCC] O157 E Coli
>
>Tim, and all
>
>There is talk that E Coli test should replace the Fecal Coliform test 
>because if one should start with a compost low in human pathogens 
>(yardwaste) and it ends up as low after heating phase, it really doesn't 
>matter if the temperatures got to proper temperature and time because 
>there was no problem to begin with. That may be very well for public 
>health reasons but IMO we need to also reduce plant pathogens like 
>nematodes, sudden oak death, pine pitch and dutch elm disease and so 
>many more.  I think this is better done using Fecal coliform as the 
>indicator (as it is now) because there would be more starting bacteria 
>and would be in all types of compost. If the heat process reduces them 
>to < 1000 per gram we can be more assure both plant and human pathogens 
>have been reduced.
>
>Perhaps a process could be for a composter to test at the end of the 
>heat phase, keep the compost active until they get the results back. If 
>it fails, wait and retest until it passes. That way all the compost 
>going to curing would have passed the test. Also; if the USCC would 
>approve results from State Approved local water labs that test for FC 
>all the time for drinking water the composters could test more often and 
>get results back sooner without the potential problem of samples 
>changing during  travel. I think instruction should be given to the lab 
>doing the test to make sure the dilutions are optimized to have the 1000 
>per gram range be in the section of the MPN range that is most detailed. 
>We are not looking for counts - just pass/fail.
>
>Frank
>
>
>
>
>
>Tim Evans wrote:
>
>  
>
>>Alan,
>>
>>The extensive UKWIR research
>>http://www.ukwir.org/site/web/content/reports/reports?SubFolders=90083&Fold
>>    
>>
>e
>  
>
>>rId=90078&SubFolderId=90083 showed that E. coil O157 has a similar
>>thermo-tolerance to indigenous E. coli.  This was a big concern because
>>there had been reports that it was more thermo-tolerant than "normal E.
>>coli" but this was proved to be wrong - the earlier researchers had used a
>>cultured laboratory strain as their reference and because of its "pampered"
>>existence this culture was less thermo-tolerant than indigenous E. coil -
>>i.e. the stuff that we healthy animals excrete every day.  The research
>>    
>>
>also
>  
>
>>confirmed indigenous E. coil is a good indicator for other bacterial
>>pathogens and that using such as Salmonella Senftenberg is unnecessary -
>>indeed I can't see how the conditions inside a microcosm used to contain
>>    
>>
>the
>  
>
>>S. Senftenberg can possibly mimic conditions in the bulk of the material
>>being treated.  
>>
>>I agree with the 503 Class-A and Class-B standards and used them before
>>there was anything comparable this side of the Pond. However there is also
>>    
>>
>a
>  
>
>>question of diligence - the dung from an animal infected with O157:H7
>>contains up to log-8 E. coli per gram dry solids.  The infective dose for a
>>human [with low defence] is 10[?].  If I was treating manure that could
>>    
>>
>have
>  
>
>>O157 I would look at the intended use [and the reasonably expected misuse]
>>for the product.  Thankfully, a tiny minority of humans have O157
>>    
>>
>infection;
>  
>
>>the same cannot be said for farm animals so that is why I would be more
>>cautious with manure than sewage sludge.  
>>
>>When, in 1995, I embarked on bagging biosolids composted with straw and
>>selling it to gardeners via garden center retailers, I was concerned to
>>    
>>
>meet
>  
>
>>the highest standards and we used Class-A / PFRP.  We gave hygiene
>>instructions on the bags about handwashing but it is reasonable to expect
>>some will ignore this.  Also children might be around it.  We had a QA
>>system for time temperature and sidelined any that did not meet it - this
>>went to broad-acre agriculture small-grain cereal production.  We verified
>>the QA time-temperature with E. coli testing - to verify that the Critical
>>Control Point's Critical Limits were appropriate.  But, this was a 'high
>>risk' use so Class-A was essential. [we could have labelled, but didn't
>>"when you have handled chicken, please wash your hands before touching my
>>compost" -:) ]
>>
>>On a note of good news, Protozoa in soil love gram negative bacteria so
>>    
>>
>when
>  
>
>>the E. coli, Salmonella et al. land on soil the Protozoa think "it's
>>breakfast time", graze them and multiply. 
>>
>>regards
>>
>>Tim
>> 
>>
>>    
>>
>
>  
>

-- 
Frank Shields
Soil Control Lab
42 Hangar way
Watsonville, CA  95076
(831) 724-5422 tel
(831) 724-3188 fax
frank at compostlab.com
www.compostlab.com