WBR0051
| 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. |
| 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:: |