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Does STEC release heat-stable exotoxins into food?


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#1 schnitzelman

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Posted 15 July 2016 - 11:06 PM

I can't find anything definitive online

 

Sorry, the title is supposed to read:

 

Does STEC release exotoxins into food that are heat-stable and can the toxins make people sick after being heated to high temperatures?

 

I am specifically talking about STEC, not botulinum or perfringens etc



#2 Charles.C

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Posted 16 July 2016 - 12:52 AM

 

Sorry, the title is supposed to read:

(a) Does STEC release exotoxins into food that are heat-stable and (b) can the toxins make people sick after being heated to high temperatures?

I am specifically talking about STEC, not botulinum or perfringens etc

 

 

Hi Schnitzelman,

 

For interested readers, some general background on STEC (Shiga toxin producing [pathogenic]E.coli)(eg E.coli O157:H7 bacterium) here -

 

http://www.about-eco..._symptoms_risks

 

Stec Prevention Strategies

Because STEC-associated HUS is a relatively rare disease, widespread vaccination of human populations at risk may not be cost-effective. One possible vaccination strategy involves immunization of cattle to reduce the prevalence of STEC colonization, thereby reducing the likelihood of STEC entering the food chain. A clinical trial was recently conducted in feedlot cattle that tested the efficacy of immunization against secreted E. coli O157:H7 proteins in reducing prevalence of E. coli O157:H7 shedding [26]. The average proportion of cattle shedding E. coli O157:H7 in vaccine-treated pens (8.8%) was significantly lower (P = .04) than in nonvaccinated pens (21.3%). Ultimately, expansion of vaccine efforts of this type may prevent colonization and shedding of multiple pathogenic STEC serotypes, thereby diminishing food contamination before it reaches consumers.

 

A recent example demonstrates how widespread this contamination can be, as well as how routine microbiologic testing performed by government regulatory agencies can be beneficial. In June 2002, the ConAgra Beef Company issued a nationwide recall of ground beef products when routine microbiologic testing performed by the US Department of Agriculture revealed STEC contamination [27]. If widely consumed, the recalled meat could have caused an epidemic of massive proportions: contaminated meat consumed before the national recall was implicated in a small, contained epidemic of Shiga toxin—producing E. coli infection that was clustered in Colorado and that involved residents of 6 other states. Even in this small epidemic, ⩾5 cases of HUS occurred.

 

Clearly, the food safety practice of cooking ground beef to 72°C (160°F), or until meat is no longer pink, has been widely adopted by the fast-food industry, contributing to the decrease in STEC infections traced to this vehicle. This practice is perhaps not as consistently followed by the private consumer who enjoys rare hamburger, although it is possible that ground beef irradiation may allow these consumers to eat rare hamburger with impunity. Although it is unreasonable to advocate avoidance of fresh fruits and vegetables that may be contaminated at the farm level as a prevention measure, it is practical to educate consumers about food-safety practices that would limit contamination of uncooked foods within the consumer kitchen. These measures include using separate utensils and cutting surfaces to prepare raw meats and frequent hand washing. Until effective HUS prevention and treatment strategies are developed, limiting consumer exposure to STEC remains important.

 

http://cid.oxfordjou.../38/9/1298.full

 

 

(a) Yes, but may depend on the specific toxin (ie stx1,stx2) / the meaning of  "high temperature" / the time for which heat applied.

stx2 variants appear considered as more related to illness than stx1.

 

(b) For stx2 variants, apparently depends on specific toxin variant / temperatures / time. See 2nd pdf, Pgs 498-500, Fig4

 

Attached File  shiga-like toxin from E.coli.pdf   46.98KB   7 downloads

(general comment)

 

Attached File  Shiga toxin,2009.pdf   560.36KB   6 downloads

(more detailed toxin comments)

 

Attached File  Shiga toxin 2 variants from pathogenic E.coli,2012.pdf   674.92KB   5 downloads

Recent epidemiological and molecular typing studies indicate that STEC strains producing Stx2 have been associated more closely with the severe human disease conditions HUS and hemorrhagic colitis than STEC strains producing Stx1 [8,9].

Nucleotide and amino acid sequence analyses have revealed three distinct Stx1 variants, Stx1a, Stx1c, and Stx1d [10–13]. In contrast to the Stx1 variants, a diverse and heterogeneous group of seven distinct variants of the Stx2 have been identified [14–20].

 

Note - HUS = Haemolytic Uraemic Syndrome


Kind Regards,

 

Charles.C


#3 schnitzelman

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Posted 16 July 2016 - 01:22 AM

Let's say 82°C

 

Thanks, I did read something similar to that pdf. Have there been any reported cases of illness due to this particular scenario?



#4 Charles.C

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Posted 16 July 2016 - 01:27 AM

Let's say 82°C

 

Thanks, I did read something similar to that pdf. Have there been any reported cases of illness due to this particular scenario?

 

the 2nd pdf discusses toxin pasteurization stability.

the 3rd pdf (eg Fig4) has data regarding toxin thermal stability/toxicity up to 100degC.

 

If one assumes a worst possible option, looks like the toxin is heat stable and active up to 100degC (time variable unspecified).


Kind Regards,

 

Charles.C





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