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{{WBRQuestion
{{WBRQuestion
|QuestionAuthor=William J Gibson
|QuestionAuthor=William J Gibson (Reviewed by Yazan Daaboul)
|ExamType=USMLE Step 1
|ExamType=USMLE Step 1
|MainCategory=Microbiology
|MainCategory=Microbiology
Line 8: Line 8:
|MainCategory=Microbiology
|MainCategory=Microbiology
|SubCategory=Genitourinary, General Principles, Infectious Disease
|SubCategory=Genitourinary, General Principles, Infectious Disease
|MainCategory=Microbiology
|MainCategory=Microbiology
|MainCategory=Microbiology
|MainCategory=Microbiology
|MainCategory=Microbiology
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|MainCategory=Microbiology
|MainCategory=Microbiology
|SubCategory=Genitourinary, General Principles, Infectious Disease
|SubCategory=Genitourinary, General Principles, Infectious Disease
|Prompt=A 22-year-old woman presents to her primary care physician complaining of dysuria for the past 3 days with mild urethral discharge. Her last unprotected sexual encounter was 2 weeks ago. Gram stain of the urethral swab reveals gram-negative diplococci. Which of the following media could be used to isolate this organism?
|Prompt=A 22-year-old woman presents to her primary care physician complaining of dysuria and mucopurulent urethral discharge for the past 3 days. She states that she had unprotected sexual encounter 2 weeks prior to presentation. Gram stain of the urethral swab reveals gram-negative diplococci. Which of the following media may be used to isolate organism causing this patient's condition?
|Explanation=The patient in this vignette has been infected with [[Neisseria gonorrhea]], a gram negative diplococcus. [[Neisseria gonorrhea]] is the second most common sexually transmitted illness behind chlamydia. Because both organisms cause [[dysuria]] and discharge, they are hard to differentiate without culture results. Whereas [[Chlamydia trachomatis]] is usually detected with nucleic acid based assays, [[Neisseria gonorrhea]] can be cultured with Thayer-Martin media. Due to the high rate of co-infection and clinical difficulty in distinguishing the two organisms, proper treatment requires [[ceftriaxone]] (for gonorrhea coverage) and [[azithromycin]] (for chlamydia coverage).
|Explanation=The patient in this vignette has been infected with [[''Neisseria gonorrhea'']], a gram negative diplococcus. [[''Neisseria gonorrhea'']] is the second most common sexually transmitted infection after ''Chlamydia trachomatis''.
|AnswerA=Thayer-Martin
 
|AnswerAExp=[[Neisseria gonorrhea]] is a gram-negative diploccocus whose infection constitutes the second most common sexually transmitted illness. Gonorrhea infection often presents as [[dysuria]] accompanied by purulent discharge.
Because both organisms cause [[dysuria]] and urethral discharge, they may be difficult to differentiate without culture results. Nonetheless, ''[[N. gonorrhea]]'' is classically associated with a mucopurulent or purulent urethral discharge, Whereas [[''Chlamydia trachomatis'']] is associated with a more clear or mucoid discharge. [[''N. gonorrhea'']] may be cultured with Thayer-Martin media. Due to the high rate of co-infection when patients present with ''N. gonorrhea'' urethritis, proper treatment requires coverage for both ''N. gonorrhea'' and ''C. trachomatis'' using ceftriaxone and azithromycin to cover both organisms, respectively.
|AnswerB=Maconkey’s Agar
|AnswerA=Thayer-Martin agar
|AnswerBExp=Maconkey’s agar is used to culture a variety of organisms. Lactose-fermenting enterics (eg [[Escherichia coli]]) will appear as pink colonies.
|AnswerAExp=[[''Neisseria gonorrhea'']] is a gram-negative diploccocus whose infection constitutes the second most common sexually transmitted illness. Gonorrhea infection often presents as [[dysuria]] accompanied by purulent urethral discharge.
|AnswerB=MacConkey’s Agar
|AnswerBExp=Maconkey’s agar (MAC) is used to culture a variety of gram-negative organisms. Lactose-fermenting enterics (eg [[''Escherichia coli'']]) will appear as pink colonies.
|AnswerC=Tellurite Agar
|AnswerC=Tellurite Agar
|AnswerCExp=Tellurite agar can be use to culture [[Corynebacterium diptheria]].
|AnswerCExp=Tellurite agar may be use to culture [[''Corynebacterium diptheriae'']].
|AnswerD=Bordet-Genou Agar
|AnswerD=Bordet-Genou Agar
|AnswerDExp=Bordet-Genou agar is used to culture [[Bordetella pertussis]].
|AnswerDExp=Bordet-Genou agar is used to culture [[''Bordetella pertussis'']].
|AnswerE=Sabouraud’s agar
|AnswerE=Sabouraud’s agar
|AnswerEExp=Sabouraud’s agar is used to culture [[fungi]].
|AnswerEExp=Sabouraud’s agar is used to culture [[fungi]].
|EducationalObjectives=[[Gonorrhea]] infection often presents as [[dysuria]] accompanied by purulent discharge.
|EducationalObjectives=[[''Neisseria gonorrhea'']] is a sexually transmitted infection that often presents as [[dysuria]] accompanied by purulent urethral discharge. It grows on Thayer-Martin agar. Treatment consists of ceftriaxone to cover ''N. gonorrhea'', along with azithromycin for concomitant coverage of a presumed ''Chlamydia trachomatis'' co-infection.
|References=First Aid 2014 page 137
|References=First Aid 2014 page 137


http://www.cdc.gov/nchhstp/newsroom/docs/STD-Trends-508.pdf
|RightAnswer=A
|RightAnswer=A
|WBRKeyword=Sexually transmitted infection, STI, STD, Gonorrhea, Microbiology, Bacteria, Laboratory
|WBRKeyword=Sexually transmitted infection, STI, STD, Gonorrhea, Microbiology, Bacteria, Laboratory
|Approved=Yes
|Approved=Yes
}}
}}

Revision as of 17:11, 1 August 2014
Author PageAuthor::William J Gibson (Reviewed by Yazan Daaboul)
Exam Type ExamType::USMLE Step 1
Main Category MainCategory::Microbiology
Sub Category SubCategory::Genitourinary, SubCategory::General Principles, SubCategory::Infectious Disease
Prompt [[Prompt::A 22-year-old woman presents to her primary care physician complaining of dysuria and mucopurulent urethral discharge for the past 3 days. She states that she had unprotected sexual encounter 2 weeks prior to presentation. Gram stain of the urethral swab reveals gram-negative diplococci. Which of the following media may be used to isolate organism causing this patient's condition?]]
Answer A AnswerA::Thayer-Martin agar
Answer A Explanation [[AnswerAExp::''Neisseria gonorrhea'' is a gram-negative diploccocus whose infection constitutes the second most common sexually transmitted illness. Gonorrhea infection often presents as dysuria accompanied by purulent urethral discharge.]]
Answer B AnswerB::MacConkey’s Agar
Answer B Explanation [[AnswerBExp::Maconkey’s agar (MAC) is used to culture a variety of gram-negative organisms. Lactose-fermenting enterics (eg ''Escherichia coli'') will appear as pink colonies.]]
Answer C AnswerC::Tellurite Agar
Answer C Explanation [[AnswerCExp::Tellurite agar may be use to culture ''Corynebacterium diptheriae''.]]
Answer D AnswerD::Bordet-Genou Agar
Answer D Explanation [[AnswerDExp::Bordet-Genou agar is used to culture ''Bordetella pertussis''.]]
Answer E AnswerE::Sabouraud’s agar
Answer E Explanation [[AnswerEExp::Sabouraud’s agar is used to culture fungi.]]
Right Answer RightAnswer::A
Explanation [[Explanation::The patient in this vignette has been infected with ''Neisseria gonorrhea'', a gram negative diplococcus. ''Neisseria gonorrhea'' is the second most common sexually transmitted infection after Chlamydia trachomatis.

Because both organisms cause dysuria and urethral discharge, they may be difficult to differentiate without culture results. Nonetheless, N. gonorrhea is classically associated with a mucopurulent or purulent urethral discharge, Whereas ''Chlamydia trachomatis'' is associated with a more clear or mucoid discharge. ''N. gonorrhea'' may be cultured with Thayer-Martin media. Due to the high rate of co-infection when patients present with N. gonorrhea urethritis, proper treatment requires coverage for both N. gonorrhea and C. trachomatis using ceftriaxone and azithromycin to cover both organisms, respectively.
Educational Objective: ''Neisseria gonorrhea'' is a sexually transmitted infection that often presents as dysuria accompanied by purulent urethral discharge. It grows on Thayer-Martin agar. Treatment consists of ceftriaxone to cover N. gonorrhea, along with azithromycin for concomitant coverage of a presumed Chlamydia trachomatis co-infection.
References: First Aid 2014 page 137]]

Approved Approved::Yes
Keyword WBRKeyword::Sexually transmitted infection, WBRKeyword::STI, WBRKeyword::STD, WBRKeyword::Gonorrhea, WBRKeyword::Microbiology, WBRKeyword::Bacteria, WBRKeyword::Laboratory
Linked Question Linked::
Order in Linked Questions LinkedOrder::
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