WBR0053
| 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 microbiologist has been given a number of unknown clinical samples and is attempting to visualize organisms by gram stain. Which of the following organisms will he be unable to visualize with this method? |
| Answer A | AnswerA::Strep Pyogenes |
| Answer A Explanation | AnswerAExp::Incorrect - Strep Pyogenes is a gram positive coccus. |
| Answer B | AnswerB::H. Influenza |
| Answer B Explanation | AnswerBExp::Incorrect - H. Influenza is a gram negative rod. |
| Answer C | AnswerC::Bacteriodes Fragilis |
| Answer C Explanation | AnswerCExp::Incorrect - Bacteriodes Fragilis is a gram negative rod. |
| Answer D | AnswerD::Legionella Pneumophila |
| Answer D Explanation | AnswerDExp::Correct - See Explanation |
| Answer E | AnswerE::Corynebacterium Diptheria |
| Answer E Explanation | AnswerEExp::Incorrect - Corynebacterium Diptheria is a gram positive rod. |
| Right Answer | RightAnswer::D |
| Explanation | [[Explanation::Legionella Pneumophila is a primarily intracellular organism which gram stains poorly. The stain of choice for Legionella is a silver stain. Legionella infections cause atypical pneumonia and are associated with aerosols from contaminated water, such as certain air conditioning systems. The treatment of choice is a macrolide (eg erythromycin).
Educational Objective: Legionella Pneumophila is a primarily intracellular organism which gram stains poorly. The stain of choice for Legionella is a silver stain.
References :First Aid 2012 page 162
Tags :#Microbiology #Biochemistry |
| Approved | Approved::Yes |
| Keyword | WBRKeyword::WJG |
| Linked Question | Linked:: |
| Order in Linked Questions | LinkedOrder:: |