microbiology chapter 12 test bank

Correct Answer: D

Rationale: The correct answer is D: Proteus vulgaris. Non-lactose-fermenting, Gram-negative rods that produce gas in a nutrient broth are characteristic of Proteus species. Proteus vulgaris is known for its swarming motility and ability to produce hydrogen sulfide gas. Salmonella typhi and Shigella dysenteriae are Enterobacteriaceae that do not produce gas in a nutrient broth. Escherichia coli is a lactose-fermenting bacterium and would not be expected to produce gas in a nutrient broth.

Correct Answer: A

Rationale: Step 1: Small, curved Gram-negative bacilli with a monotrichous flagellum point towards a motile bacterium. Step 2: The absence of spores or capsules and preference for alkaline conditions further narrows down the possibilities. Step 3: Vibrio cholerae fits all criteria as it is a curved, motile, Gram-negative bacillus that thrives in alkaline environments. Summary: Escherichia coli is a facultative anaerobe, Salmonella and Shigella are non-flagellated, and all of them can form capsules or spores, unlike Vibrio cholerae.

Correct Answer: A

Rationale: 1. Vaccination introduces antigens to stimulate immune response. 2. T and B cells are activated to produce memory cells for long-lasting protection. 3. Active immunity develops over time post-vaccination. 4. Choice A is correct as it accurately describes the process and outcomes. 5. Choice B is incorrect as it contradicts the process of active immunity. 6. Choice C is incorrect as the process of active immunity is consistent regardless of the situation. 7. Therefore, the correct answer is A as it aligns with the mechanism and characteristics of artificial active immunity.

Correct Answer: A

Rationale: The correct answer is A: Antitoxic serum. In the neutralization reaction to identify botulinum toxin, antitoxic serum is used to neutralize the toxin in white mice. Antitoxic serum contains antibodies that specifically target and neutralize the botulinum toxin. Normal serum (B) does not contain the necessary antibodies to neutralize the toxin. Antibacterial serum (C) is not effective against toxins like botulinum. Diagnosticum (D) is a general term and does not specifically refer to the biological product required for this reaction.

Correct Answer: B

Rationale: The correct answer is B: Agglutination reaction. This is the most suitable serological reaction for the quick determination of the antigen of the epizootic agent causing mass rodent deaths. In agglutination reaction, antibodies cause the clumping of antigens, allowing for easy visual detection of the presence of the specific antigen. This is efficient for rapid diagnosis in cases of suspected infectious diseases like plague. A: Precipitation reaction is more suitable for identifying soluble antigens, not for quick determination of a specific antigen in this scenario. C: Reaction of passive hemagglutination is used for measuring the presence of antibodies, not antigens. D: Bordet-Gengou test is a specific test for the identification of Bordetella pertussis bacterium, not suitable for this scenario.