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|Prompt=After isolating and purifying several bacterial toxins using thiol-disulfide exchange affinity chromatography, a researcher studying the properties of bacterial toxins exposes the purified product to a number of harsh conditions. In one experiment, he heats the product to 70 °C and then injects a sample into anesthetized rats. Which of the following bacterial toxins is likely to elicit symptoms after injection?
|Prompt=After isolating and purifying several bacterial toxins using thiol-disulfide exchange affinity chromatography, a researcher studying the properties of bacterial toxins exposes the purified product to a number of harsh conditions. In one experiment, he heats the product to 70 °C and then injects a sample into anesthetized rats. Which of the following bacterial toxins is likely to elicit symptoms after injection?
|Explanation=[[Staphylococcal enterotoxin B]] is an exotoxin, produced by ''[[Staphylococcus aureus]]'', that is often associated with food poisoning. This exotoxin can be encountered in contaminated meat and dairy products where the conditions are optimal for ''[[Staphylococcus aureus]]'' to thrive. Enterotoxin B has been shown to withstand temperatures as high as 100 °C for several minutes, long after the bacteria have been destroyed. [[Staphylococcal enterotoxin B]]'s ability to withstand high temperatures is atypical of exotoxins, which are often extremely heat labile and usually do not tolerate heat fluctuations. [[Staphylococcal enterotoxin B]] is resistant to the gut proteases, enabling it to cause disease shortly after ingestion. Beyond regular food poisoning, [[Staphylococcal enterotoxin B]] possesses a super-antigen quality, leading to [[toxic shock syndrome]] (TSS) by crosslinking MHCII to TCRs with great affinity.
|Explanation=[[Staphylococcal enterotoxin B]] is an exotoxin, produced by ''[[Staphylococcus aureus]]'', that is often associated with food poisoning. This exotoxin can be encountered in contaminated meat and dairy products where the conditions are optimal for ''[[Staphylococcus aureus]]'' to thrive. Enterotoxin B has been shown to withstand temperatures as high as 100 °C for several minutes, long after the bacteria have been destroyed. [[Staphylococcal enterotoxin B]]'s ability to withstand high temperatures is atypical of exotoxins, which are often extremely heat labile and usually do not tolerate heat fluctuations. [[Staphylococcal enterotoxin B]] is resistant to the gut proteases, enabling it to cause disease shortly after ingestion. Beyond regular food poisoning, [[Staphylococcal enterotoxin B]] possesses a super-antigen quality, leading to [[toxic shock syndrome]] (TSS) by crosslinking MHCII to TCRs with great affinity.
|AnswerA=Pseudomonas aeruginosa Exotoxin A
|AnswerA=''Pseudomonas aeruginosa'' Exotoxin A
|AnswerAExp=The Pseudomonas aeruginosa Exotoxin A typically cannot withstand  a few minutes of heating to 60 °C.
|AnswerAExp=The ''Pseudomonas aeruginosa'' Exotoxin A is usually inactivated by heating at 60 °C for several minutes.
|AnswerB=Vibrio cholerae exotoxin
|AnswerB=''Vibrio cholerae'' exotoxin
|AnswerBExp=The Vibrio cholerae exotoxin typically cannot withstand a few minutes of heating to 60 °C.
|AnswerBExp=The ''Vibrio cholerae'' exotoxin is usually inactivated by heating at 60 °C for several minutes.
|AnswerC=Staphylococcal Enterotoxin B
|AnswerC=Staphylococcal Enterotoxin B
|AnswerCExp=Staphylococcal enterotoxin B is unique among exotoxins for being very heat stable withstanding temperatures as high as 100 C for several minutes.
|AnswerCExp=Staphylococcal enterotoxin B is unique among exotoxins for being very heat stable withstanding temperatures as high as 100 C for several minutes.
|AnswerD=Tetanospasmin
|AnswerD=Tetanospasmin
|AnswerDExp=Tetanospasmin typically cannot withstand a few minutes of heating to 60 °C.
|AnswerDExp=Tetanospasmin is usually inactivated by heating at 60 °C for several minutes.
|AnswerE=Bordetella pertussis Exotoxin
|AnswerE=''Bordetella pertussis'' Exotoxin
|AnswerEExp=The Bordetella pertussis Exotoxin typically cannot withstand a few minutes of heating to 60 °C.
|AnswerEExp=The ''Bordetella pertussis'' Exotoxin is usually inactivated by heating at 60 °C for several minutes.
|References=<br>
|References=<br>
Balaban N, Rasooly A. Staphylococcal enterotoxins. International Journal of Food Microbiology. 2000;61(1):1-10.
Balaban N, Rasooly A. Staphylococcal enterotoxins. International Journal of Food Microbiology. 2000;61(1):1-10.
|RightAnswer=C
|RightAnswer=C
|WBRKeyword=''[[Staphylococcus aureus]]'', Staphylococcal enterotoxin B, Heat-stable exotoxin
|WBRKeyword=''[[Staphylococcus aureus]]'', Staphylococcal enterotoxin B, Heat-stable exotoxin, toxin, staph, food-borne illness, toxic shock syndrome,
|Approved=Yes
|Approved=Yes
|EducationalObjective=[[Staphylococcal enterotoxin B]] is able to withstand high temperatures and temperature fluctuations, which is atypical for the majority of exotoxins.
|EducationalObjective=[[Staphylococcal enterotoxin B]] is able to withstand high temperatures and temperature fluctuations, which is atypical for the majority of exotoxins.
}}
}}

Revision as of 13:23, 29 August 2014
Author [[PageAuthor::Serge Korjian M.D. (Reviewed by Alison Leibowitz)]]
Exam Type ExamType::USMLE Step 1
Main Category MainCategory::Microbiology
Sub Category SubCategory::General Principles
Prompt [[Prompt::After isolating and purifying several bacterial toxins using thiol-disulfide exchange affinity chromatography, a researcher studying the properties of bacterial toxins exposes the purified product to a number of harsh conditions. In one experiment, he heats the product to 70 °C and then injects a sample into anesthetized rats. Which of the following bacterial toxins is likely to elicit symptoms after injection?]]
Answer A AnswerA::''Pseudomonas aeruginosa'' Exotoxin A
Answer A Explanation AnswerAExp::The ''Pseudomonas aeruginosa'' Exotoxin A is usually inactivated by heating at 60 °C for several minutes.
Answer B AnswerB::''Vibrio cholerae'' exotoxin
Answer B Explanation AnswerBExp::The ''Vibrio cholerae'' exotoxin is usually inactivated by heating at 60 °C for several minutes.
Answer C AnswerC::Staphylococcal Enterotoxin B
Answer C Explanation AnswerCExp::Staphylococcal enterotoxin B is unique among exotoxins for being very heat stable withstanding temperatures as high as 100 C for several minutes.
Answer D AnswerD::Tetanospasmin
Answer D Explanation AnswerDExp::Tetanospasmin is usually inactivated by heating at 60 °C for several minutes.
Answer E AnswerE::''Bordetella pertussis'' Exotoxin
Answer E Explanation AnswerEExp::The ''Bordetella pertussis'' Exotoxin is usually inactivated by heating at 60 °C for several minutes.
Right Answer RightAnswer::C
Explanation [[Explanation::Staphylococcal enterotoxin B is an exotoxin, produced by Staphylococcus aureus, that is often associated with food poisoning. This exotoxin can be encountered in contaminated meat and dairy products where the conditions are optimal for Staphylococcus aureus to thrive. Enterotoxin B has been shown to withstand temperatures as high as 100 °C for several minutes, long after the bacteria have been destroyed. Staphylococcal enterotoxin B's ability to withstand high temperatures is atypical of exotoxins, which are often extremely heat labile and usually do not tolerate heat fluctuations. Staphylococcal enterotoxin B is resistant to the gut proteases, enabling it to cause disease shortly after ingestion. Beyond regular food poisoning, Staphylococcal enterotoxin B possesses a super-antigen quality, leading to toxic shock syndrome (TSS) by crosslinking MHCII to TCRs with great affinity.

Educational Objective:
References:
Balaban N, Rasooly A. Staphylococcal enterotoxins. International Journal of Food Microbiology. 2000;61(1):1-10.]]

Approved Approved::Yes
Keyword [[WBRKeyword::Staphylococcus aureus]], WBRKeyword::Staphylococcal enterotoxin B, WBRKeyword::Heat-stable exotoxin, WBRKeyword::toxin, WBRKeyword::staph, WBRKeyword::food-borne illness, WBRKeyword::toxic shock syndrome
Linked Question Linked::
Order in Linked Questions LinkedOrder::
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