microbiology basic and clinical principles test bank

Correct Answer: D

Rationale: The correct answer is D because all of the mentioned bacteria (Escherichia coli, Salmonella enterica, and Pseudomonas aeruginosa) are gram-negative bacteria that produce endotoxins in their cell walls. Endotoxins are released when the bacteria are destroyed, leading to the activation of the immune system and potentially causing septic shock. Escherichia coli and Salmonella enterica are common causes of gastrointestinal infections, while Pseudomonas aeruginosa is known for causing infections in immunocompromised individuals. Therefore, all three bacteria can produce endotoxins that contribute to septic shock. Choices A, B, and C are incorrect because each of these bacteria individually can produce endotoxins that lead to septic shock.

Correct Answer: A

Rationale: The correct answer is A: Metronidazole. Rationale: 1. Metronidazole is the drug of choice for amebic dysentery due to its effectiveness against the causative agent, Entamoeba histolytica. 2. Metronidazole has good tissue penetration and is able to reach the site of infection in the gut. 3. It is a bactericidal drug that acts by disrupting the DNA structure of the parasite. 4. Metronidazole is well-absorbed orally and has minimal side effects. Summary of other choices: B: Furazolidonum - Not the drug of choice for amebic dysentery. It is primarily used for treating bacterial diarrhea. C: Levomycetin - Not effective against Entamoeba histolytica and not recommended for amebic dysentery. D: Phthalazol - Not commonly used for amebic dysentery treatment. Metronidazole is preferred due

Correct Answer: B

Rationale: The correct answer is B: Vibrio cholerae. Cholera is caused by Vibrio cholerae, a bacterium that infects the small intestine, leading to severe diarrhea and dehydration. This bacterium produces a toxin that causes the symptoms of cholera. A: Shigella dysenteriae causes dysentery, not cholera. C: Salmonella enterica causes food poisoning, not cholera. D: Escherichia coli can cause food poisoning but not cholera.

Correct Answer: C

Rationale: The correct answer is C because infectious (non-sterile) immunity is achieved through the persistence of the infectious agent in the body, allowing the immune system to continuously recognize and combat the pathogen. This type of immunity provides long-lasting protection against future infections by the same agent. Choice A (cross-reactivity of antibodies) is incorrect as it refers to the ability of antibodies to recognize similar antigens, not necessarily related to infectious immunity. Choice B (toxemia and formation of antitoxic antibodies) is incorrect as it specifically relates to toxins produced by pathogens and the corresponding antibody response, not the persistence of the infectious agent itself. Choice D (neutralization of infectious agent) is incorrect as it describes the process of antibodies binding to and inactivating pathogens, but it does not necessarily lead to long-term immunity through the persistence of the infectious agent.

Correct Answer: B

Rationale: The correct answer is B: Simpler. Prokaryotic cytoplasm is simpler than eukaryotic cytoplasm because prokaryotic cells lack membrane-bound organelles such as a nucleus, mitochondria, and endoplasmic reticulum that are present in eukaryotic cells. Prokaryotic cytoplasm contains fewer components and structures compared to eukaryotic cytoplasm, making it less complex. Therefore, the prokaryotic cytoplasm is simpler in structure. Choices A, C, and D are incorrect because prokaryotic cytoplasm is not more complex than eukaryotic cytoplasm, there is a clear difference in structure between prokaryotic and eukaryotic cytoplasm, and the statement "None of the above" is not accurate as the correct answer is B.