Anthrax vs diphtheria – identify the shared feature: Which statement correctly describes a key commonality between disease caused by Corynebacterium diphtheriae and Bacillus anthracis?
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ABoth organisms are Gram-positive spore formers
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BDiphtheria toxin and anthrax edema toxin are both ADP-ribosylating toxins
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CThe most serious clinical manifestations are primarily the direct result of toxin action
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DBoth organisms cause only respiratory tract infections (not skin disease)
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EBoth are obligate intracellular pathogens
Answer
Correct Answer: The most serious clinical manifestations are primarily the direct result of toxin action
Explanation
Introduction / Context:Differentiating organisms by their virulence strategies is a staple of medical microbiology. Corynebacterium diphtheriae and Bacillus anthracis are distinct bacteria, yet both deploy potent exotoxins that drive the major clinical outcomes of their respective diseases.
Given Data / Assumptions:
- C. diphtheriae produces diphtheria toxin that halts host protein synthesis.
- B. anthracis produces edema toxin (adenylate cyclase activity) and lethal toxin (MAPKK protease).
- Severe disease outcomes (e.g., pseudomembrane-mediated airway compromise in diphtheria; shock/edema in systemic anthrax) reflect toxin effects.
Concept / Approach:Focus on the role of toxins rather than microbial growth characteristics. Diphtheria’s systemic complications (myocarditis, neuropathies) are toxin-mediated. Anthrax toxins cause edema, immune dysregulation, and shock; these toxemic effects are central to severity. Hence, the key shared feature is toxin-driven pathology.
Step-by-Step Solution:Confirm that diphtheria manifestations correlate with circulating toxin levels.Recognize that anthrax lethality is tied to edema/lethal toxins acting systemically.Select the option emphasizing toxin-mediated severe disease.
Verification / Alternative check:Antitoxin therapy in diphtheria and toxin-targeted strategies in experimental anthrax highlight the centrality of toxins in driving serious outcomes.
Why Other Options Are Wrong:
- Gram-positive spore formers: C. diphtheriae is non-spore-forming.
- Both ADP-ribosylating: diphtheria toxin is; anthrax edema toxin is an adenylate cyclase, not ADP-ribosylating.
- Only respiratory infections: both can cause cutaneous disease; statement is false as written.
- Obligate intracellular: neither is obligate intracellular.
Common Pitfalls:Confusing toxin enzymology across pathogens; assuming organism traits (e.g., spore formation) are shared based on Gram positivity alone.
Final Answer:The most serious clinical manifestations are primarily the direct result of toxin action.