WBR0252
| Author | [[PageAuthor::Ogheneochuko Ajari, MB.BS, MS [1] (Reviewed by Alison Leibowitz)]] |
|---|---|
| Exam Type | ExamType::USMLE Step 1 |
| Main Category | MainCategory::Microbiology |
| Sub Category | SubCategory::Infectious Disease |
| Prompt | [[Prompt::A 28-year-old female presents to the physicians office with complaints of vaginal odor, itching, pain, and discharge. A thin gray homogeneous fluid that is adherent to the vaginal mucosa is observed during physical examination. The labia, introitus, cervix, and cervical discharge appear normal. Microscopic examination of the discharge demonstrates clue cells, with a PH greater than 5 and dominant gram-negative cells. Which of the following is the likely etiologic agent?]] |
| Answer A | AnswerA::''Gardnerella vaginalis'' |
| Answer A Explanation | [[AnswerAExp::Gardnerella vaginalis is the causative agent of bacterial vaginosis presenting as a gray vaginal discharge with a fishy smell, clue cells, and a vaginal pH greater than 4.5.]] |
| Answer B | AnswerB::''Candida albicans'' |
| Answer B Explanation | [[AnswerBExp::Candida albicans are yeasts with pseudohyphae and hyphae that form germ tubes at 37 °C in serum.]] |
| Answer C | AnswerC::''Trichomonas vaginalis'' |
| Answer C Explanation | [[AnswerCExp::Trichomonas vaginalis, often sexually transmitted, may cause foul-smelling greenish discharge, itching, and burning. Trichomonas vaginalis is displayed as motile trophozoites in a methylene blue wet mount, and demonstrates corkscrew motility.]] |
| Answer D | AnswerD::''Neisseria gonorrhea'' |
| Answer D Explanation | [[AnswerDExp::Neisseria gonorrhea is a gram-negative, kidney bean-shaped diplococci that can cause creamy purulent vaginal discharge.]] |
| Answer E | AnswerE::''Chlamydia trachomatis'' |
| Answer E Explanation | [[AnswerEExp::Chlamydia trachomatis, an obligate intracellular bacterium that cannot make ATP, is gram-negative. In adults, it often causes urethritis, cervicitis, pelvic inflammatory disease, and inclusion conjunctivitis, while in neonates, it causes inclusion conjunctivitis and neonatal pneumonia.]] |
| Right Answer | RightAnswer::A |
| Explanation | [[Explanation::The patient in this scenario has Bacterial vaginosis, caused by Gardnerella vaginalis. Gardnerella vaginalis is a facultative anaerobic gram-negative (pleomorphic) rod, which is catalase and oxidase negative. It works synergistically with other normal flora organisms such as lactobacillus, mobiluncus, bacteroides and peptostreptococcus. Gardnerella vaginalis flourishes with an increased vaginal pH of > 4.5. Diagnostic indications include clue cells (epithelial cells covered with bacteria), a vaginal pH > 4.5, gray homogenous discharge, and upon a Whiff test with KOH, a “fishy” amine odor. Infection may follow menses or antibiotic therapy. Bacterial vaginosis is frequently treated with Metronidazole or Clindamycin. Educational Objective: Gardnerella vaginalis, a gram-negative rod, is the causative agent of bacterial vaginosis, which presents as a thin, gray, homogenous fluid with clue cells and a vaginal pH greater than 4.5. |
| Approved | Approved::Yes |
| Keyword | |
| Linked Question | Linked:: |
| Order in Linked Questions | LinkedOrder:: |