WBR294
| Author | PageAuthor::Gerald |
|---|---|
| Exam Type | ExamType::USMLE Step 1 |
| Main Category | MainCategory::Microbiology |
| Sub Category | SubCategory::Gastrointestinal |
| Prompt | [[Prompt::A 28-year-old male presents to the clinic with abdominal cramps, general malaise, fever, and diarrhea 6 hours after consuming ground beef. Few leukocytes are found in his fecal specimen. Growth of colorless colonies on sorbitol-MacConkey agar is noted. The pathogen produces toxins which contains an enzymatic subunit that interferes with protein synthesis. Which of the following antibiotics has a similar mechanism regarding to the toxin's action on translation?]] |
| Answer A | AnswerA::Linezolid. |
| Answer A Explanation | AnswerAExp::Linezolid and aminoglycosides block the formation of initiation complex, thereby inhibiting protein synthesis. |
| Answer B | AnswerB::Tetracycline. |
| Answer B Explanation | AnswerBExp::Correct. Tetracycline blocks the entry and binding of aminoacyl transfer RNA, thereby inhibiting protein synthesis. |
| Answer C | AnswerC::Quinupristin/dalfopristin. |
| Answer C Explanation | AnswerCExp::Quinupristin/dalfopristin and other streptogramins block peptidyl transferase which forms peptide bonds between adjacent amino acids using tRNAs during the translation process. |
| Answer D | AnswerD::Clindamycin. |
| Answer D Explanation | AnswerDExp::Clindamycin and macrolides block translocation by binding to the 50S rRNA of the large bacterial ribosome subunit. |
| Answer E | AnswerE::Chloramphenicol. |
| Answer E Explanation | AnswerEExp::Chloramphenicol blocks peptidyl transferase which forms peptide bonds between adjacent amino acids using tRNAs during the translation process. |
| Right Answer | RightAnswer::B |
| Explanation | [[Explanation::E. coli O157:H7 is negative for invasiveness (Sereny test), adheres through the E. coli common pilus (ECP), and does not produce heat-stable or heat-labile toxins. In addition, E. coli O157:H7 is usually sorbitol negative, whereas most of all E. coli with human origin ferment sorbitol. Among the virulence factors, Shiga-like toxins (SLTs) are iron-regulated toxins that catalytically cleaves N-glycoside bond of adenine in 28S rRNA of the 60S ribosome unit to prevent aminoacyl tRNA binding, thereby inhibiting protein synthesis. Educational Objective: |
| Approved | Approved::No |
| Keyword | WBRKeyword::Protein synthesis |
| Linked Question | Linked:: |
| Order in Linked Questions | LinkedOrder:: |