WBR0054
| 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.
References: First Aid 2012 page 152.
Tags: #Microbiology #Pathophysiology |
| Approved | Approved::Yes |
| Keyword | |
| Linked Question | Linked:: |
| Order in Linked Questions | LinkedOrder:: |