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|QuestionAuthor=William J Gibson
|QuestionAuthor=William J Gibson
|ExamType=USMLE Step 1
|ExamType=USMLE Step 1
|MainCategory=Microbiology
|SubCategory=Head and Neck, Neurology, General Principles, Infectious Disease
|MainCategory=Microbiology
|SubCategory=Head and Neck, Neurology, General Principles, Infectious Disease
|MainCategory=Microbiology
|SubCategory=Head and Neck, Neurology, General Principles, Infectious Disease
|MainCategory=Microbiology
|MainCategory=Microbiology
|SubCategory=Head and Neck, Neurology, General Principles, Infectious Disease
|MainCategory=Microbiology
|SubCategory=Head and Neck, Neurology, General Principles, Infectious Disease
|MainCategory=Microbiology
|SubCategory=Head and Neck, Neurology, General Principles, Infectious Disease
|MainCategory=Microbiology
|SubCategory=Head and Neck, Neurology, General Principles, Infectious Disease
|MainCategory=Microbiology
|MainCategory=Microbiology
|SubCategory=Head and Neck, Neurology, General Principles, Infectious Disease
|Prompt=A 5 year old boy from rural Africa has recently immigrated to the United States with his family.  He presents to your office with a fever of 100.7 F, fatigue, and severe pharyngitis.  Physical exam reveals marked cervical lymphadenopathy, and pseudomembranes in the throat.  A throat swab is performed which reveals gram positive bacilli.  What is the mechanism of action of the toxin produced by the causative organism?   
|Prompt=A 5 year old boy from rural Africa has recently immigrated to the United States with his family.  He presents to your office with a fever of 100.7 F, fatigue, and severe pharyngitis.  Physical exam reveals marked cervical lymphadenopathy, and pseudomembranes in the throat.  A throat swab is performed which reveals gram positive bacilli.  What is the mechanism of action of the toxin produced by the causative organism?   
|Explanation=This patient is suffering from an infection by Corynebacterium Diptheriae, a gram positive rod which has mostly been eradicated in the developed world through vaccination.  Diptheria causes upper respiratory tract infections with sore throat and low-grade fever.  The hallmark of this infection is an adherent true membrane on the tonsils referred to as pseudomembranes.
|Explanation=This patient is suffering from an infection by Corynebacterium Diptheriae, a gram positive rod which has mostly been eradicated in the developed world through vaccination.  Diptheria causes upper respiratory tract infections with sore throat and low-grade fever.  The hallmark of this infection is an adherent true membrane on the tonsils referred to as pseudomembranes.

Revision as of 00:46, 2 July 2013

 
Author PageAuthor::William J Gibson
Exam Type ExamType::USMLE Step 1
Main Category MainCategory::Microbiology
Sub Category SubCategory::Head and Neck, SubCategory::Neurology, SubCategory::General Principles, SubCategory::Infectious Disease
Prompt [[Prompt::A 5 year old boy from rural Africa has recently immigrated to the United States with his family. He presents to your office with a fever of 100.7 F, fatigue, and severe pharyngitis. Physical exam reveals marked cervical lymphadenopathy, and pseudomembranes in the throat. A throat swab is performed which reveals gram positive bacilli. What is the mechanism of action of the toxin produced by the causative organism?]]
Answer A AnswerA::Inactivate 60S ribsosome by cleaving rRNA
Answer A Explanation AnswerAExp::Incorrect - This is the mechanism of the toxin produced by Shigella and EHEC.
Answer B AnswerB::Activates adenylate cyclase by stimulating Gs
Answer B Explanation AnswerBExp::Incorrect - This is the mechanism of the toxin produced by Vibrio Cholera
Answer C AnswerC::Activates adenylate cyclase by disabling Gi
Answer C Explanation AnswerCExp::Incorrect - This is the mechanism of the toxin produced by Bordetella Pertusis.
Answer D AnswerD::Cleaves SNARE protein
Answer D Explanation AnswerDExp::Incorrect - This is the mechanism of Botulinum and Tetanus toxin, which disables neurotransmitter release at the synaptic cleft.
Answer E AnswerE::Inactivate EF-2
Answer E Explanation AnswerEExp::Correct - See Explanation
Right Answer RightAnswer::E
Explanation [[Explanation::This patient is suffering from an infection by Corynebacterium Diptheriae, a gram positive rod which has mostly been eradicated in the developed world through vaccination. Diptheria causes upper respiratory tract infections with sore throat and low-grade fever. The hallmark of this infection is an adherent true membrane on the tonsils referred to as pseudomembranes.


Educational Objective: Diptheria toxin causes disease by inactivating Elongation Factor 2 (EF-2). Diptheria infection can be diagnosed by the presence of pseudomembranes in the throat.

References: First Aid 2012 page 152. Tags: #Microbiology #Pathophysiology
Educational Objective:
References: ]]

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