WBR0507
| Author | [[PageAuthor::Gonzalo A. Romero, M.D. (Reviewed by Alison Leibowitz)]] |
|---|---|
| Exam Type | ExamType::USMLE Step 1 |
| Main Category | MainCategory::Embryology, MainCategory::Microbiology, MainCategory::Pharmacology |
| Sub Category | SubCategory::Infectious Disease |
| Prompt | [[Prompt::A 2-year-old girl is brought to the pediatrician because her mother is concerned about her teeth appear abnormally dark. She states that her daughter developed a ring-like rash on her leg after a nature walk, which appeared to be similar to a rash that her 17-year-old son developed following a camping trip. The mother administered her daughter the leftover antibiotics that had been prescribed to her teenage son for his rash. Which of the following mechanisms of action corresponds to the antibiotic most likely provided to the young girl?]] |
| Answer A | AnswerA::Prevents attachment of aminoacyl-tRNA |
| Answer A Explanation | AnswerAExp::See overall explanation |
| Answer B | AnswerB::Inhibits the formation of initiation complex |
| Answer B Explanation | [[AnswerBExp::This is the mechanism of action of aminoglycosides used for gram negative rod infections.]] |
| Answer C | AnswerC::Inhibits protein synthesis by binding to the 50S ribosomal subunit |
| Answer C Explanation | [[AnswerCExp::This is the mechanism of action of macrolides, used to treat atypical pneumonias (Mycoplasma, Chlamydia, Legionella), URiI, STDs, gram-positive cocci (streptococcal infections in patients allergic to penicillin), and Neisseria.]] |
| Answer D | AnswerD::Inhibits the translocation of the peptidyl-tRNA |
| Answer D Explanation | [[AnswerDExp::This often corresponds with aminoglycosides use.]] |
| Answer E | AnswerE::Inhibits protein elongation by blocking peptidyl-transferase |
| Answer E Explanation | [[AnswerEExp::This is the mechanism of action associated with chloramphenicol.]] |
| Right Answer | RightAnswer::A |
| Explanation | [[Explanation::In this scenario a 2-year-old patient presents with discolored teeth. She took an antibiotic during pregnancy to treat Lyme’s disease. The treatment of choice of Lyme disease is tetracycline, which is contraindicated in pregnancy due to bone and teeth malformation. Tetracycline, specifically doxycycline inhibits the protein synthesis by binding to the 30S ribosomal subunit and preventing the aminoacyl-tRNA attachment.
 Educational Objective: When tetracycline is administered to young children, it is often associated with teeth discoloration (teratogenic) |
| Approved | Approved::Yes |
| Keyword | |
| Linked Question | Linked:: |
| Order in Linked Questions | LinkedOrder:: |