Medical Microbiology Test Bank

Correct Answer: A

Rationale: Rationale: 1. Dysenteric amoeba (Choice A) is the correct answer because it can exist asymptomatically in carriers and be transmitted through cysts. 2. Malarial plasmodium (Choice B) causes malaria, not carried asymptomatically in cysts. 3. Intestinal trichomonad (Choice C) causes trichomoniasis, not carried asymptomatically in cysts. 4. Dermatotropic leishmania (Choice D) causes skin lesions, not carried asymptomatically in cysts.

Correct Answer: B

Rationale: The correct answer is B: Spirochete. Lyme disease is caused by the bacterium Borrelia burgdorferi, which is a spirochete. Spirochetes are spiral-shaped bacteria that move by rotating like a corkscrew, which is characteristic of Borrelia burgdorferi. A: Spirillum - Spirillum bacteria are helical-shaped but are not the causative agent for Lyme disease. C: Vibrio - Vibrio bacteria are curved or comma-shaped and are not associated with Lyme disease. D: Diplococcus - Diplococcus bacteria are spherical-shaped and typically occur in pairs, not the causative agent for Lyme disease. Therefore, the correct answer is B because Borrelia burgdorferi is a spirochete bacterium that causes Lyme disease.

Correct Answer: C

Rationale: The correct answer is C: ensure survival under harsh conditions. Bacterial endospores are dormant, resistant structures that form under adverse conditions to protect the bacterial DNA and allow the bacterium to survive extreme environments. This function is crucial for the bacterium's long-term survival. Choice A is incorrect as endospores do not directly produce exotoxins. Choice B is incorrect as endospores do not store nutrients but rather protect the bacterium's genetic material. Choice D is incorrect as endospores do not enhance motility but rather enable survival during unfavorable conditions.

Correct Answer: B

Rationale: The correct answer is B because the presence of calcium dipicolinate in bacterial spores helps protect their DNA from damage under harsh conditions. Calcium dipicolinate acts as a stabilizer, preserving the spore structure. Choice A is incorrect as bacterial spores have a tough protein coat, not a lipid-rich membrane. Choice C is incorrect as bacterial spores have very low metabolic activity. Choice D is incorrect as bacterial spores have low water content to prevent damage during harsh conditions.

Correct Answer: A

Rationale: The correct answer is A: Wasserman test, IFT. The patient's symptoms of diffuse alopecia and Pinkus' sign are suggestive of secondary syphilis. The Wasserman test and Immunofluorescence Test (IFT) are used to detect antibodies against Treponema pallidum, the bacterium causing syphilis. This would confirm or rule out syphilis as the underlying cause of the patient's symptoms. Choice B (T.pallidum Immobilization Test) is similar to the Wasserman test but less commonly used. Choice C (Detection of the nasal mucous membrane for M.leprae) is irrelevant as leprosy does not present with the described symptoms. Choice D (Consultation of neuropathist) is premature without ruling out syphilis first. Thus, the Wasserman test, IFT should be the initial examination to investigate the likely cause of the patient's symptoms.