microbiology test bank

Correct Answer: C

Rationale: Step 1: The nucleocapsid is the structure containing the viral genome and the protein capsid. Step 2: The genome carries the genetic material of the virus. Step 3: The capsid is the protein coat that encloses and protects the viral genome. Step 4: Therefore, the correct answer is C: Genome and capsid. Summary: A: Capsid and spikes - Incorrect, spikes are not part of the nucleocapsid. B: Genome and envelop - Incorrect, the envelop is not part of the nucleocapsid. D: Capsid and envelope - Incorrect, the envelope is not part of the nucleocapsid.

Correct Answer: C

Rationale: The correct answer is C (25�C) because dimorphic fungi typically grow as molds at lower temperatures. At 25�C, the fungus is likely in its mold phase, which is the preferred temperature range for mold growth. Choices A, B, and D are incorrect because 15�C and 20�C are too low for optimal mold growth, and 37�C is too high as it typically favors the yeast phase of dimorphic fungi. Therefore, the preferred temperature for mold growth of a dimorphic fungus is 25�C.

Correct Answer: A

Rationale: Rationale: A: Early application of gentamicin is not recommended as a specific treatment for C. difficile-associated post antibiotic diarrhea because it does not have efficacy against C. difficile. B: Metronidazole is recommended as first-line treatment for mild to moderate C. difficile infection. C: Stopping antibiotic treatment and observing the clinical response for 48 hours is not a recommended strategy as prompt treatment is crucial in C. difficile infection. D: Vancomycin per os is an appropriate treatment for severe C. difficile infection. In summary, A is incorrect because gentamicin is not effective against C. difficile, while B, C, and D are potential treatment strategies based on severity of the infection.

Correct Answer: A

Rationale: The correct answer is A because penicillins and cephalosporins inactivate transpeptidase activity of penicillin binding proteins, leading to disruption of bacterial cell wall synthesis. This mechanism makes them bactericidal, not bacteriostatic (choice B). Choice C is incorrect as penicillins and cephalosporins target cell wall synthesis, not the cytoplasmic membrane. Choice D is incorrect as option A is the correct statement.

Correct Answer: A

Rationale: Step 1: Chlorhexidine belongs to the group of biguanides, making choice A accurate. Step 2: It is commonly used for disinfection of hands, skin, and mucous membranes. Step 3: It has a broad spectrum of antimicrobial activity, making it widely applicable. Summary: Choice B is incorrect as chlorhexidine is not classified as an alcohol. Choice C is incorrect as chlorhexidine has various applications. Choice D is incorrect as chlorhexidine is generally safe for use with low toxicity.