medical microbiology test bank

Correct Answer: D

Rationale: The correct answer is D because all three bacteria listed can produce toxins that cause severe diarrhea. Clostridium difficile produces toxins that can lead to antibiotic-associated diarrhea, Vibrio cholerae produces a toxin that causes cholera, and certain strains of Escherichia coli produce toxins that result in severe diarrhea. Therefore, choosing option D is correct because all the mentioned bacteria can cause severe diarrhea. Options A, B, and C are incorrect individually because each bacterium listed can produce a toxin resulting in severe diarrhea.

Correct Answer: D

Rationale: The correct answer is D because fungi do not form flagella. Fungi reproduce sexually and asexually (A) through spores, have a cell wall (B) made of chitin, and are mostly aerobic or facultative anaerobes (C). Flagella are structures found in some protozoa and bacteria, not in fungi. Therefore, option D is the only statement that is not true about fungi.

Correct Answer: C

Rationale: The correct answer is C because both Mycobacterium bovis and Mycobacterium tuberculosis are bacteria that can cause tuberculosis in humans. Mycobacterium bovis primarily infects animals but can be transmitted to humans, while Mycobacterium tuberculosis is the main causative agent of tuberculosis in humans. Therefore, both choices A and B are correct. Choice D is incorrect because we know that Mycobacterium bovis and Mycobacterium tuberculosis are causative agents of tuberculosis in humans.

Correct Answer: C

Rationale: The correct answer is C: Polar placement of volutin granules. This feature is indicative of Corynebacterium diphtheria. Volutin granules are metachromatic granules found in the polar region of the bacterial cell, which is characteristic of this species. This feature helps differentiate it from other bacteria. Explanation: A: Fence-like position of the agent's cells is not a specific morphologic feature of Corynebacterium diphtheria. B: Spores that exceed cells in diameter is not a characteristic feature of Corynebacterium diphtheria. D: Presence of the capsule is not a distinguishing morphologic feature of Corynebacterium diphtheria. In summary, the polar placement of volutin granules is the most indicative feature for determining the type of agent as Corynebacterium diphtheria, making it the correct choice.

Correct Answer: A

Rationale: The correct answer is A: chloroplasts. Algae and plant cells have chloroplasts, which are responsible for photosynthesis. This organelle contains chlorophyll, enabling these cells to convert sunlight into energy. Mitochondria (B) are found in all eukaryotic cells, not specific to algae and plants. Vacuoles (C) are present in plant cells but also in other eukaryotic cells. Vesicles (D) are membrane-bound sacs found in all types of cells for transport and storage purposes, not unique to algae and plants. Therefore, A is the correct answer.