E. coli (ETEC)
Enteropathogenic E. coli (EPEC)
E. coli (EIEC)
E. coli (EHEC)
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.
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 .)
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 )
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.
eco1 - E.coli Procedure, MFO-18,2003.pdf 1.66MB
eco2 - E.coli guidance,2012.pdf 578.92KB
eco3 - FSIS, generic e.coli etc,pathogen reduction rule 1996.pdf 1.34MB
eco4 - isolation-detection Pathogenic E.coli in foods,2015.pdf 700.51KB