microbiology test bank

Correct Answer: B

Rationale: The correct answer is B because antigenic drift is not caused by the exchange of genetic information between animal and human influenza viruses. Antigenic drift is actually due to point mutations in the genes that encode for the surface proteins of the virus, leading to small changes in the antigens. These mutations can affect the hemagglutinin of both type A and B influenza viruses, making choices A and C correct. Choice D is incorrect because antigenic drift can occur in both type A and B influenza viruses, with type B being less prone to drift compared to type A.

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: D

Rationale: The correct answer is D: Gram-negative bacteria without peptidoglycan. Chlamydia is an intracellular, gram-negative bacteria that lacks peptidoglycan in its cell wall. Peptidoglycan is a key component of the cell wall in most bacteria, but Chlamydia has a unique structure without it. This makes it different from choices A, B, and C, which describe characteristics not applicable to Chlamydia. Choice A is incorrect because Chlamydia is not a gram-positive coccobacteria. Choice B is incorrect because Chlamydia does have a cell wall, albeit lacking peptidoglycan. Choice C is incorrect because Chlamydia is not a gram-negative bacteria with little peptidoglycan, but rather without it.

Correct Answer: B

Rationale: The correct answer is B: Staphylococcus aureus. This bacteria is known to cause skin infections and toxic shock syndrome due to its ability to produce toxins that can lead to severe symptoms. Staphylococcus aureus is commonly found on the skin and can enter the body through cuts or wounds, causing infections. Other choices are incorrect because Pseudomonas aeruginosa typically causes infections in immunocompromised individuals, Micrococcus luteus is a common skin bacterium that is not typically pathogenic, and Propionibacterium acnes is associated with acne, not skin infections or toxic shock syndrome.

Correct Answer: D

Rationale: The correct answer is D: Fifth disease. Rubella virus is associated with Fifth disease, also known as erythema infectiosum. It is caused by parvovirus B19, not rubella virus. Mumps (choice A) is caused by the mumps virus. Roseola (choice B) is caused by human herpesvirus 6 or 7. Rubeola (choice C) is the scientific name for measles, caused by the measles virus. Therefore, the correct answer is Fifth disease as it is the disease associated with rubella virus.