Anthrax vs diphtheria – identify the shared feature: Which statement correctly describes a key commonality between disease caused by Corynebacterium diphtheriae and Bacillus anthracis?

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.