WBR0047

Author	PageAuthor::William J Gibson
Exam Type	ExamType::USMLE Step 1
Main Category	MainCategory::Microbiology, MainCategory::Pathology
Sub Category	SubCategory::General Principles, SubCategory::Infectious Disease
Prompt	Prompt::A 25 year old male presents to his primary care physician complaining of a painless chancre on his penis. The causal organism can be identified by which of the following stains?
Answer A	AnswerA::Giemas stain
Answer A Explanation	AnswerAExp::Incorrect - Giemsa stain is used to identify Borellia, Plasmodium and Chlamydia.
Answer B	AnswerB::Carbol-fuschin
Answer B Explanation	AnswerBExp::Incorrect - Carbol-fuschin (also known as Ziehl-Neelsen stain) is used to identify acid fast organisms. Syphillis is not an acid-fast organism.
Answer C	AnswerC::Silver stain
Answer C Explanation	AnswerCExp::Incorrect - Silver stain is used to identify Fungi such as pneumocystis carinii.
Answer D	AnswerD::Fluorescent antibody
Answer D Explanation	AnswerDExp::Correct - Treponema Pallidum can be identified using a Fluorescent Treponemal Antibody Absorption (FTA-Abs) assay. This assay is more specific than the Rapid Plasmin Reagin (RPR) or VDRL tests for Syphillus.
Answer E	AnswerE::India Ink
Answer E Explanation	AnswerEExp::Incorrect - India ink is used to visualize Cryptococcus Neoformans.
Right Answer	RightAnswer::D
Explanation	[[Explanation::The patient has primary syphillus, characterized by a painless chancre (an ulcer-like lesion). Syphillis is caused by the spirochete Treponema Pallidum and can be identified by darkfield microscopy or flourescent antibody staining. The fluorescent Treponemal Antibody Absorption (FTA-Abs) assay is more specific than the Rapid Plasmin Reagin (RPR) or VDRL tests for Syphillus. None of the other answer choices could be used to visualize Treponema. Educational Objective: Primary syphillis is caused by Treponema Pallidum which can be identified by Fluorescent antibody staining. References: First Aid 2012 page 165. Educational Objective: References: ]]
Approved	Approved::Yes
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