False about C. diphtheriae
**Question:** False about C. diphtheriae
A. C. diphtheriae produces a toxin that causes paralysis
B. C. diphtheriae is susceptible to penicillin
C. C. diphtheriae is a non-motile bacterium
D. C. diphtheriae is a harmless commensal organism
**Core Concept:** C. diphtheriae is the causative agent of diphtheria, an infectious disease characterized by inflammation, ulceration, and obstruction of respiratory tract. Diphtheria is caused by the production of diphtheria toxin, which is responsible for the clinical manifestations and complications of the disease.
**Why the Correct Answer is Right:** C. diphtheriae is indeed pathogenic, but the correct answer "D" is right because diphtheria is a disease caused by this bacterium, not because it is harmless. The toxin produced by C. diphtheriae, however, is what makes the bacterium pathogenic. Diphtheria toxin causes inflammation, ulceration, and obstruction of respiratory tract, leading to severe complications if left untreated.
**Why Each Wrong Option is Incorrect:**
A. Although diphtheria toxin can cause paralysis in severe cases, the answer is incorrect because C. diphtheriae itself is the causative agent, not the toxin.
B. C. diphtheriae is not susceptible to penicillin, which is a common antibiotic used to treat bacterial infections, including diphtheria. Penicillin is effective against a wide range of bacteria but has no effect on C. diphtheriae due to its resistance mechanisms.
C. C. diphtheriae is a motile bacterium, meaning it has flagella that allow it to move around. This option is incorrect because diphtheriae is motile, not harmless.
**Clinical Pearl:** Diphtheria is a vaccine-preventable disease that was once a significant global health concern. Vaccination is crucial in protecting against diphtheria, as well as other bacterial infections. It is essential for healthcare professionals and medical students to understand the distinction between the bacterium and the toxin it produces, as well as the importance of vaccination for preventing diphtheria and other infectious diseases.