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Toxins - types and heat resistance


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#1 rita

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Posted 19 November 2009 - 07:26 AM

I would like to get more knowledge on the toxins. I know of exo,endo,entero toxins but I am really confused. Which toxins are heat labile and stable etc. Based on this I can get more understanding on toxin producing pathogens.



Thanks a lot in advance.



#2 Jean

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Posted 19 November 2009 - 10:01 AM

Dear Rita,



I am just mentioning the toxins related to food poisoning. Please correct me if I am wrong and hopefully others can add to it.



There are basically 2 groups of bacterial toxins, namely, exotoxins and endotoxins.



Exotoxins are produced by the pathogens in food after they have multiplied to excess numbers.

Endotoxins are released in the host’s body during cell lysis or multiplication during an infection. (If I am not wrong, endotoxins are heat stable)



Different types of toxins infect different sites of the human body.



- Enterotoxin affects the intestinal cells

- Neurotoxin affects the nerve cells

- Cytotoxins affect the mucosal cells.



Bacteria and their kinds of toxins



1) Salmonella produce endotoxins.

2) Bacillus cereus produces exotoxins. 2 types- Diarrheal type (enterotoxin) & highly heat stable emetic type toxin

3) Cl.botulinum produces exotoxins which is a neurotoxin (toxins are inactivated by heating at 75oC -80oC). Out of 3 kinds of botulism only one kind is Food botulism.

4) Cl.perfringes produces exotoxins.

5) S.aureus produces staphylococcal enterotoxins which is an exotoxin. This toxin is not inactivated or denatured by cooking or boiling for 30 minutes.

6) V.cholerae O:1 & O:139 produces enterotoxins (Cholera Toxin) which again is an exotoxins which is heat labile

7) E.coli, there are 4 categories in which diarrheagenic E.coli can be placed :-

-Shiga toxin producing E.coli (STEC) and also enterohaemorrhagic E.coli strains (EHEC) – These produce shiga-like toxins or verocytotoxins

-Enterotoxigenic E.coli (ETEC)–These produce heat labile or heat stable enterotoxin

-Diarrheagenic E.coli also called as Enteropathogenic E.coli (EPEC)which do not produce any enterotoxins or shiga-like toxins.

-Enteroinvasive E.coli. (EIEC)

Other groups or categories are present but not significant to food borne diseases.

8)Shigella dysenteriae produce shiga toxins

9)Y.enterocolitica produce enterotoxin and the toxin is heat stable
Best regards,

J

Only the curious will learn and only the resolute overcome the obstacles to learning. The quest quotient has always excited me more than the intelligence quotient. Eugene S Wilson

#3 Rizwan Ahmed

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Posted 19 November 2009 - 11:14 AM

thanks Jean its quite helpful and informative :)


regards.

Riz



#4 MRios

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Posted 20 November 2009 - 03:14 PM

And then you have your micotoxins, which can give you all kinds of interesting diseases, like neural tube defects in newborns, hepatic disease and even cancer.
http://en.wikipedia.org/wiki/Mycotoxin






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