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{{WBRQuestion
{{WBRQuestion
|QuestionAuthor={{Rim}}
|QuestionAuthor={{Rim}}, {{AJL}} {{Alison}}
|ExamType=USMLE Step 1
|ExamType=USMLE Step 1
|MainCategory=Microbiology, Pathophysiology
|MainCategory=Microbiology, Pathophysiology
Line 20: Line 20:
|MainCategory=Microbiology, Pathophysiology
|MainCategory=Microbiology, Pathophysiology
|SubCategory=Neurology, Infectious Disease
|SubCategory=Neurology, Infectious Disease
|Prompt=A 34 year-old man was brought to the hospital by his son for severe nausea, vomiting and abdominal cramps. The patient had noticeable trouble speaking so his son provided the history. He explained that his father started complaining of blurred vision and difficulty swallowing a short time after he had his dinner. Upon exam, you note generalized weakness, bilateral ptosis, and facial muscle drooping. Vital signs were stable but the patient seems to be hypoventilating. The patient's saturation drops rapidly and he requires emergent intubation. Upon further questioning, the son reports that his father had eaten some canned red peppers his mother had prepared at home. Which of the following steps is likely to be inhibited in this patient?
|Prompt=A 34-year-old male is brought to the emergency room by his sister for severe nausea, vomiting, and abdominal cramps. The patient has difficulty speaking, so his sister explains that her brother began complaining of blurred vision and difficulty swallowing after his dinner of home-canned red peppers. Upon physical examination, you note generalized weakness, bilateral ptosis, facial muscle drooping, and hyperventilation. The patient's saturation drops rapidly requiring emergent intubation. Which of the following steps is likely inhibited in this patient?


[[Image:Synapse_q.jpg|600px]]
[[Image:Synapse_q.jpg|600px]]
|Explanation=Clostridium botulinum is a gram positive spore forming bacillus that produces an exotoxin known as the botulinum toxin. Clostridium botulinum thrives in anaerobic conditions and foodborne illness occurs due to the ingestion of preformed botulinum toxin usually found in home canned vegetables prepared without following required methods. Infant botulism is seen in babies less than 12 months that are fed honey that contains the bacteria. Botulinum toxin is inactivated by high temperatures, so boiling home-canned food for 10 minutes prior to eating is preferred.
|Explanation=''[[Clostridium botulinum]]'', a Gram-positive spore forming bacillus, produces an exotoxin referred to as the botulinum toxin. ''[[Clostridium botulinum]]'' thrives in anaerobic conditions, and food-borne illness occurs following the ingestion of the botulinum toxin, frequently from home-canned vegetables prepared without following standard safety  methods. Infant botulism frequently manifests in infants fed honey containing the bacteria. Botulinum toxin is inactivated by high temperatures.


Botulinum toxin acts by blocking acetylcholine vesicle release from the pre-synaptic cleft leading to flaccid paralysis of all muscles including the diaphragm.
Botulinum toxin acts by blocking the acetylcholine vesicle release from the pre-synaptic cleft, leading to flaccid paralysis of all muscles.


Educational objective: Botulinum toxin inhibits acetylcholine vesicles from being release in the pre-synaptic cleft leading to flaccid paralysis. It is produced by Clostridium botulinum an anaerobic gram positive bacillus.
|EducationalObjectives= Botulinum toxin acts by blocking the acetylcholine vesicle release from the pre-synaptic cleft, leading to flaccid paralysis of all muscles. It is produced by ''[[Clostridium botulinum]]'', an anaerobic Gram-positive bacillus.
 
|References= Cherington M. Clinical spectrum of botulism. Muscle Nerve. 1998;21(6):701-10.


References:
Cherington M. Clinical spectrum of botulism. Muscle Nerve. 1998;21(6):701-10.
|AnswerA=A
|AnswerA=A
|AnswerAExp=This refers to neurotransmitter integration into vesicles. Reserpine and vesamicol usually act by inhibiting vesicle formation. Botulinum has no effect on vesicle formation.
|AnswerAExp=This refers to neurotransmitter integration into vesicles. Reserpine and vesamicol act by inhibiting vesicle formation, but botulinum has no effect on vesicle formation.
|AnswerB=B
|AnswerB=B
|AnswerBExp=This refers to vesicle release into the synaptic cleft inhibited in botulism. The botulinum toxin prevents the release of acetylcholine containing vesicles leading to flaccid paralysis.
|AnswerBExp=This refers to vesicle release into the synaptic cleft inhibited in botulism. The botulinum toxin prevents the release of acetylcholine containing vesicles, leading to flaccid paralysis.
|AnswerC=C
|AnswerC=C
|AnswerCExp=This refers to neurotransmitter binding to specific receptors on the post-synaptic membrane. Neurotransmitter antagonists can exert their effect by this mechanism.
|AnswerCExp=This refers to a neurotransmitter binding to specific receptors on the post-synaptic membrane. Neurotransmitter antagonists often use this mechanism.
|AnswerD=D
|AnswerD=D
|AnswerDExp=This refers to neurotransmitter degradation. Acetylcholinersterase inhibitors act by inhibiting the breakdown of acetylcholine at the synaptic cleft. Cocaine has a different mechanism of action.
|AnswerDExp=This refers to neurotransmitter degradation. Acetylcholinesterase inhibitors act by hindering the breakdown of acetylcholine at the synaptic cleft.
|AnswerE=E
|AnswerE=E
|AnswerEExp=This refers to the reuptake of neurotransmitters, usually inhibited by substances like amphetamines and cocaine. Reuptake inhibition is not seen in botulism.
|AnswerEExp=This refers to the re-uptake of neurotransmitters, which is inhibited by amphetamines and cocaine.
|RightAnswer=B
|RightAnswer=B
|WBRKeyword=Clostridium botulinum, Botulism, Neurotransmitter,
|WBRKeyword=Clostridium botulinum, Botulism, Neurotransmitter, mechanism of action, neuroscience, neurology,
|Approved=No
|Approved=Yes
}}
}}

Revision as of 19:14, 31 July 2014
Author [[PageAuthor::Rim Halaby, M.D. [1], Alison Leibowitz [2] (Reviewed by Alison Leibowitz)]]
Exam Type ExamType::USMLE Step 1
Main Category MainCategory::Microbiology, MainCategory::Pathophysiology
Sub Category SubCategory::Neurology, SubCategory::Infectious Disease
Prompt [[Prompt::A 34-year-old male is brought to the emergency room by his sister for severe nausea, vomiting, and abdominal cramps. The patient has difficulty speaking, so his sister explains that her brother began complaining of blurred vision and difficulty swallowing after his dinner of home-canned red peppers. Upon physical examination, you note generalized weakness, bilateral ptosis, facial muscle drooping, and hyperventilation. The patient's saturation drops rapidly requiring emergent intubation. Which of the following steps is likely inhibited in this patient?

]]

Answer A AnswerA::A
Answer A Explanation AnswerAExp::This refers to neurotransmitter integration into vesicles. Reserpine and vesamicol act by inhibiting vesicle formation, but botulinum has no effect on vesicle formation.
Answer B AnswerB::B
Answer B Explanation AnswerBExp::This refers to vesicle release into the synaptic cleft inhibited in botulism. The botulinum toxin prevents the release of acetylcholine containing vesicles, leading to flaccid paralysis.
Answer C AnswerC::C
Answer C Explanation AnswerCExp::This refers to a neurotransmitter binding to specific receptors on the post-synaptic membrane. Neurotransmitter antagonists often use this mechanism.
Answer D AnswerD::D
Answer D Explanation AnswerDExp::This refers to neurotransmitter degradation. Acetylcholinesterase inhibitors act by hindering the breakdown of acetylcholine at the synaptic cleft.
Answer E AnswerE::E
Answer E Explanation AnswerEExp::This refers to the re-uptake of neurotransmitters, which is inhibited by amphetamines and cocaine.
Right Answer RightAnswer::B
Explanation [[Explanation::Clostridium botulinum, a Gram-positive spore forming bacillus, produces an exotoxin referred to as the botulinum toxin. Clostridium botulinum thrives in anaerobic conditions, and food-borne illness occurs following the ingestion of the botulinum toxin, frequently from home-canned vegetables prepared without following standard safety methods. Infant botulism frequently manifests in infants fed honey containing the bacteria. Botulinum toxin is inactivated by high temperatures.

Botulinum toxin acts by blocking the acetylcholine vesicle release from the pre-synaptic cleft, leading to flaccid paralysis of all muscles.
Educational Objective: Botulinum toxin acts by blocking the acetylcholine vesicle release from the pre-synaptic cleft, leading to flaccid paralysis of all muscles. It is produced by Clostridium botulinum, an anaerobic Gram-positive bacillus.
References: Cherington M. Clinical spectrum of botulism. Muscle Nerve. 1998;21(6):701-10.]]

Approved Approved::Yes
Keyword WBRKeyword::Clostridium botulinum, WBRKeyword::Botulism, WBRKeyword::Neurotransmitter, WBRKeyword::mechanism of action, WBRKeyword::neuroscience, WBRKeyword::neurology
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