WBR0076
| Author | [[PageAuthor::William J Gibson (Reviewed by Rim Halaby, M.D. [1], Jad Al Danaf, and Yazan Daaboul)]] |
|---|---|
| Exam Type | ExamType::USMLE Step 1 |
| Main Category | MainCategory::Microbiology, MainCategory::Pathology |
| Sub Category | SubCategory::Dermatology, SubCategory::General Principles, SubCategory::Infectious Disease |
| Prompt | [[Prompt::A 44-year-old man presents to the emergency department with a boil-like black ulcer which developed on his neck over the past 2 days. His past medical history is only significant for hypertension, for which he takes lisinopril daily. The patient reports he has allergies to peanuts. He denies recent travel and works in a wool-sorting factory. On physical examination, the patient's lesion is shown in the image below.
Which component of this patient's disease induces the production of TNF and IL-1?]] |
| Answer A | AnswerA::Peptidoglycan |
| Answer A Explanation | [[AnswerAExp::Peptidoglycan is composed of a sugar backbone with cross-linking by peptide side chains. It provides support for bacterial cells and protects against osmotic forces but does not directly induce IL-1 and TNF.]] |
| Answer B | AnswerB::Lipoteichoic acid |
| Answer B Explanation | [[AnswerBExp::B. anthracis is a gram-positive rod, whose lipoteichoic acid stimulates the production of IL-1 and TNF.]] |
| Answer C | AnswerC::Lipid A |
| Answer C Explanation | [[AnswerCExp::Lipid A is a molecule found on the outer membrane of gram-negative bacteria. It induces the production of TNF and IL-1, but the bacteria suspected by this clinical presentation is Bacillus anthracis, a gram-positive organism.]] |
| Answer D | AnswerD::D-Glutamate capsule |
| Answer D Explanation | [[AnswerDExp::B. anthracis is the only organism with a D-Glutamate capsule. However, its D-glutamate capsule does not induce the production of IL-1 and TNF.]] |
| Answer E | AnswerE::Glycocalyx |
| Answer E Explanation | [[AnswerEExp::The glycocalyx mediates bacterial adhesion to structures such as catheters, biological membranes, and other surfaces. It does not directly induce IL-1 and TNF.]] |
| Right Answer | RightAnswer::B |
| Explanation | [[Explanation::The patient is most likely infected with Bacillus anthracis, a gram-positive, spore-forming rod. Most patients with anthrax are exposed while working with infected animals or animal products such as wool, hides, or hair.
Inhalation anthrax can occur when a person inhales spores that are in the air (aerosolized) during the industrial processing of contaminated materials, such as wool, hides, or hair. Inhalation anthrax is alternatively called ‘Woolsorter’s Disease’. Cutaneous anthrax can occur when workers who handle contaminated animal products get spores in a cut or scrape on their skin. The lesion is usually a black eschar. Cutaneous anthrax is the most common form of anthrax infection. It is also considered to be the least dangerous. Infection usually develops from 1 to 7 days after exposure. Without treatment, cutaneous anthrax may be fatal in up to to 20% of cases. However, with proper treatment (usually ciprofloxacin or doxycycline with some restrictions), almost all patients with cutaneous anthrax survive. Because B. anthracis is a gram-positive organism, it contains lipoteichoic acid. Lipoteichoic acid, made of lipids and teichoic acid, is a component of the cell membrane induces TNF and IL-1. It is a surface-associated adhesion amphiphile that regulates the action of autolytic wall muramidases and binds to target cells at membrane phospholipids (non-specific) or at CD14 and to toll-like receptors (specific). |
| Approved | Approved::Yes |
| Keyword | WBRKeyword::Microbiology, WBRKeyword::Bacteria, WBRKeyword::Anthrax, WBRKeyword::Inflammation, WBRKeyword::Immune |
| Linked Question | Linked:: |
| Order in Linked Questions | LinkedOrder:: |
