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Trying to understand the different types of E. coli

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#1 Dr Vu

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Posted 04 September 2015 - 01:12 PM

Enterotoxigenic
E. coli
(ETEC)

Enteropathogenic E. coli (EPEC)

Enteroinvasive
E. coli
(EIEC)

Enterohemorrhagic
E. coli
(EHEC)

Enteroaggregative
E. coli
(EAEC)

 

 Can someone school me on these different types above.  if i am testing for generic Ecoli , out of the four above,which one am i testing on. i know  that it might not cover the EHEC because i normally do separate test for this one..

.

The approach recommended here permits qualitative determination of the presence of pathogenic E. coli. Aseptically weigh 25 g of sample into 225 ml of BHI broth (dilution factor of 1:10). If necessary, sample size may deviate from 25 g depending on availability of the sample, as long as the diluent is adjusted proportionally. Blend or stomach briefly. Incubate the homogenate for 10 min at room temperature with periodic shaking then allow the sample to settle by gravity for 10 min. Decant medium carefully into a sterile container and incubate for 3 h at 35°C to resuscitate injured cells. Transfer contents to 225 mL double strength TP broth in a sterile container and incubate 20 h at 44.0 ± 0.2°C. After incubation, streak to L-EMB and MacConkey agars. Incubate these agars for 20 h at 35°C.


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#2 Charles.C

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Posted 04 September 2015 - 02:39 PM

Hi Dr Vu,

 

I have seen some terminological variations but afaik, in a food context, generic E.coli usually refers to "varieties" of E.coli which are regarded as non-pathogenic.

So I guess the answer to yr query is none of the 5 groups you have listed.

 

Trick Question ? :smile:

 

PS (added) - here is a quote from a Canadian Guidance document on Beef -

 

Non-pathogenic (“generic”) strains of E. coli, when present at higher levels in the meat, may serve as indicators of fecal contamination but are only indirectly linked to  the  presence  of E. coli  O157,  being  more  generally  associated  with  the  status  of  GMP  in  a facility.

E. coli O157 is a member of the VTEC (verotoxin producing Escherichia coli) group of E. coli. [added - presumably = yr EHEC]

 

Confusingly, "generic" is also used to reference the result of classical methods to measure "E.coli" without specific regard to pathogenicity, eg from same text as above -

 

To assess the effectiveness of the sanitation system, processors should conduct routine and systematic  environmental  testing  for  an  indicator  organism(s),  such  as  Total  Aerobic Counts  (TAC)  or  generic  E.  coli.    This  will  also  help  identify  and  monitor  equipment surfaces that are difficult to clean.

The above interpretation would presumably include both pathogenic and non-pathogenic possibilities if compliant with  the classic biochemical definition of "E.coli". The primary feature which distinguishes the pathogenicity of the groups in yr OP is their virulence.

 

Personally i normally use "generic" in the top-most sense but it can evidently depend on the context. So, after reflection and for the sample you refer to, I suggest the answer to yr query might be none, any of the pathogenic groups you list other than EHEC, any pathogenic/non-pathogenic strain of "E.coli" present  in the sample. Good question although I'm curious why you wanted to know ?. :smile:


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Charles.C


#3 Dr Vu

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Posted 04 September 2015 - 02:59 PM

thnaks Charles.. we  do raw nuts and we test for generic Ecoli and 0157..I  wanted to  try to find out if i am testing for the right pathogens..


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#4 SPL

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Posted 04 September 2015 - 04:08 PM

From a biochemical metabolism aspect, the various types of e. coli you listed would be undistinguishable from  each other. Gold standard tests and quick/rapid test kits would ID suspect sample as E. coli  positive. To distinguish the listed e. coli would require genomic analysis.  


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#5 Charles.C

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Posted 04 September 2015 - 04:21 PM

thnaks Charles.. we  do raw nuts and we test for generic Ecoli and 0157..I  wanted to  try to find out if i am testing for the right pathogens..

 

Hi Dr Vu,

 

Just saw yr post. Probably the "total" "generic" E.coli is being referenced since this is the customary one seen in routine specifications, ie non-specific. I anticipate that the pathogenic E.coli O157 is normally only a small percentage of the total E.coli present. Unfortunately a small amount may already be too much.


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Charles.C


#6 FSQNNow

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Posted 07 September 2015 - 10:02 AM

For EU:  2013 is Vo. (EG) nr. 2073/2005, extended with Vo. (EU) Nr. 209/2013 (see clause 12)

ISO/TS 13136 ( 2012)Option 3 with an extension for 5 pathogen serotypes and STEC O104:H4  (see clause 12 209/2013)

 

http://eur-lex.europ...019:0023:EN:PDF

http://www.iso.org/i...?csnumber=53328

 

If you want full presentation: https://www.foodprot...ry/morabito.pdf


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#7 herdy

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Posted 16 September 2015 - 02:56 PM

Depends on how you are testing. If you are using Ecoli PF (petrifilm), none of them but any growth on the plate that is positive foe Ecoli is an indicator that pathogenic is there as well. Other testing can be done instead that will tell you if those are there.


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#8 Charles.C

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Posted 17 September 2015 - 03:07 AM

Enterotoxigenic
E. coli
(ETEC)

Enteropathogenic E. coli (EPEC)

Enteroinvasive
E. coli
(EIEC)

Enterohemorrhagic
E. coli
(EHEC)

Enteroaggregative
E. coli
(EAEC)

 

 Can someone school me on these different types above.  if i am testing for generic Ecoli , out of the four above,which one am i testing on. i know  that it might not cover the EHEC because i normally do separate test for this one..

.

The approach recommended here permits qualitative determination of the presence of pathogenic E. coli. Aseptically weigh 25 g of sample into 225 ml of BHI broth (dilution factor of 1:10). If necessary, sample size may deviate from 25 g depending on availability of the sample, as long as the diluent is adjusted proportionally. Blend or stomach briefly. Incubate the homogenate for 10 min at room temperature with periodic shaking then allow the sample to settle by gravity for 10 min. Decant medium carefully into a sterile container and incubate for 3 h at 35°C to resuscitate injured cells. Transfer contents to 225 mL double strength TP broth in a sterile container and incubate 20 h at 44.0 ± 0.2°C. After incubation, streak to L-EMB and MacConkey agars. Incubate these agars for 20 h at 35°C.

 

Hi Dr Vu,

 

I have done a bit more investigation on this topic so will attempt a little clarification of my original post regarding 2 aspects of yr OP, namely (1) interpretation of “generic” E.coli and (2) the relationship of the “generic” test to the EHEC test.

 

Query (1)

AFAIK, a "clasical"  E.coli culture is defined as, for example,  per BAM procedure ending with checking whether the  biochemical characteristics match either of Biotypes 1 and 2 (see first link below or near end of attachment eco1).

Some texts (not BAM) describe such a species  (ie either Biotypes 1 or 2) as "generic E.coli". I deduce this is the usual technical choice for Canada based on procedures recommended in attachment  eco2/Pg 38 which I anticipate are similar to that in the (Canadian) eco1 attachment below. ie for generic E.coli, Canada ~= E.coli(classical BAM).

 

Sometimes (eg see my post 2) "generic" is also used for "non-pathogenic" strains of E.coli. This is probably questionable English :smile: .)

 

Note - In contrast USA/FSIS have seemingly defined their "generic" E.coli as for Biotype 1 only (see eco3 below). Reason unknown (perhaps type 2 cases are rare in meat :unsure: )

 

Query (2)

 

The procedure you have quoted in OP is, afaik, primarily intended for the Pathogenic E.coli species which you have listed  with the exception of EHEC due this may not grow at 44degC (see eco4, pg2, 2015). This is the reason (as I think you guessed) that separate procedures for EHEC exist.

 

I doubt(?) that the procedure in OP is the preferred one for generic E.coli since less specific media are involved compared to the classical route. Some (Canadian) recommended procedures for generic E.coli are listed in eco2 (pg38) which I anticipate are similar to the procedure in attachment eco1.

 

So, afaik, for the procedure you quoted, the answer to yr OP is (as was maybe suspected) all the listed species/strains  except  EHEC.

 

Attached File  eco1 - E.coli Procedure, MFO-18,2003.pdf   1.66MB   18 downloads

Attached File  eco2 - E.coli guidance,2012.pdf   578.92KB   19 downloads

Attached File  eco3 - FSIS, generic e.coli etc,pathogen reduction rule 1996.pdf   1.34MB   15 downloads

Attached File  eco4 - isolation-detection Pathogenic E.coli in foods,2015.pdf   700.51KB   17 downloads

 

http://www.fda.gov/F...s/ucm064948.htm

http://www.fda.gov/F...s/ucm070080.htm


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Kind Regards,

 

Charles.C






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