WBR0507
| Author | [[PageAuthor::Gonzalo A. Romero, M.D. (Reviewed by Alison Leibowitz)(Reviewed by Serge Korjian)]] |
|---|---|
| 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 that her teeth have turned a dark shade of grey since her last check-up. The mother explains that her daughter has been developing normally, but she recently she started refusing formula. She also reports that approximately 1 month ago, the child had an episode of cough and sore throat for which she gave 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. Her mother had previously administered her with an antibiotic treat a rash, which was indicative of Lyme’s disease. Tetracycline, used to treat Lyme disease, is not prescribed to young children due to the high risk of bone and teeth malformation. Tetracycline, specifically doxycycline, inhibits protein synthesis by binding to the 30S ribosomal subunit and preventing the attachment of aminoacyl-tRNA.
 This image above depicts a "bull's eye" rash, often associated with Lyme disease. |
| Approved | Approved::Yes |
| Keyword | |
| Linked Question | Linked:: |
| Order in Linked Questions | LinkedOrder:: |