microbiology test bank

Correct Answer: A

Rationale: The correct answer is A: Nystatin. Nystatin is an antifungal medication, not an antibiotic used to treat bacterial infections like generalized meningococcal infection. Penicillin G, macrolides, and chloramphenicol are antibiotics commonly used to treat bacterial infections, including meningococcal infections. Penicillin G is the drug of choice for meningococcal infections, while macrolides and chloramphenicol are alternative options. Nystatin is not effective against bacteria, so it is not a suitable treatment for meningococcal infections.

Correct Answer: C

Rationale: The correct answer is C: Salmonella typhi. The patient's symptoms of diarrhea and the characteristics of non-lactose-fermenting, Gram-negative rods that are oxidase-positive and fermentative are consistent with Salmonella typhi. Salmonella typhi is the causative agent of typhoid fever, which presents with symptoms like diarrhea. Pseudomonas aeruginosa (choice A) is oxidase-positive but not fermentative. Escherichia coli (choice B) is both lactose-fermenting and oxidase-negative. Shigella dysenteriae (choice D) is oxidase-negative. Therefore, Salmonella typhi is the most likely causative agent based on the given information.

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: A

Rationale: The correct answer is A: prions. Prions are misfolded proteins that can cause spongiform encephalopathy by inducing normal proteins to misfold as well. Prions lack genetic material, distinguishing them from viruses (B), bacteria (C), and fungi (D), which all contain genetic material and cannot directly cause spongiform encephalopathy through protein misfolding.

Correct Answer: A

Rationale: The correct answer is A: Streptococcus pneumoniae. The given characteristics match this bacterium: Gram-positive diplococci, catalase-negative, and alpha-hemolytic. S. pneumoniae is a common cause of community-acquired pneumonia. Other choices are incorrect because Staphylococcus aureus is catalase-positive, Enterococcus faecalis is not alpha-hemolytic, and Klebsiella pneumoniae is not Gram-positive diplococci.