WBR0055
| Author | PageAuthor::William J Gibson |
|---|---|
| Exam Type | ExamType::USMLE Step 1 |
| Main Category | MainCategory::Microbiology |
| Sub Category | SubCategory::Musculoskeletal/Rheumatology, SubCategory::General Principles, SubCategory::Infectious Disease |
| Prompt | [[Prompt::A soldier suffers from an open leg wound after an explosion. He is treated upon returning to base, but he soon develops widespread purefaction of the wound site with bubbles arising in nearby muscle and subcutaneous tissue. What is the mechanism of the toxin in the causative organism?]] |
| Answer A | AnswerA::Bring MHCII and TCR together to stimulate leukocytes. |
| Answer A Explanation | AnswerAExp::Incorrect - this is the mechanism of the Staph Aureus Toxic Shock Syndrome toxin and Strep Pyogenes Endotoxin A. |
| Answer B | AnswerB::Phospholipase |
| Answer B Explanation | AnswerBExp::Correct - See Explanation |
| Answer C | AnswerC::Cleaves SNARE protein |
| Answer C Explanation | AnswerCExp::Incorrect - This is the mechanism of Botulinum and Tetanus toxin, which disables neurotransmitter release at the synaptic cleft. |
| Answer D | AnswerD::Inactivate 60S ribsosome by cleaving rRNA |
| Answer D Explanation | AnswerDExp::Incorrect - This is the mechanism of the toxin produced by Shigella and EHEC. |
| Answer E | AnswerE::Increases cAMP by intrinsic enzymatic activity. |
| Answer E Explanation | AnswerEExp::Incorrect - This is the mechanism of the edema factor toxin produced by Bacillus Anthracis. |
| Right Answer | RightAnswer::B |
| Explanation | [[Explanation::The patient in this vignette is suffering from gas gangrene, caused by Clostridium Perfringens. C. Perfringens is found in soil and the environment as spores, which can enter open wounds. The organism produces alpha toxin, a phospholipase which degrades cell membranes, thereby producing tissue destruction. Infections can progress rapidly, leading to myonecrosis and the formation of gas as tissue is destroyed. Potentially lethal sepsis can ensue within hours without proper treatment. The treatment for gas gangrene is wound debridement and often amputation of the affected area with adjuvant penicillin.
Educational Objective: Clostridium Perfringens produces gas gangrene and alpha toxin, a phospholipase which degrades tissues. Tags: #Microbiology #Pathophysiology |
| Approved | Approved::Yes |
| Keyword | |
| Linked Question | Linked:: |
| Order in Linked Questions | LinkedOrder:: |