microbiology a systems approach test bank

Correct Answer: B

Rationale: The correct answer is B: Mycobacterium tuberculosis. Mycobacterium tuberculosis is the bacteria responsible for causing tuberculosis. This bacterium has unique cell wall components that make it resistant to the body's immune defenses, allowing it to survive and multiply within the host. Streptococcus pyogenes (Choice A), Escherichia coli (Choice C), and Bacillus anthracis (Choice D) are not associated with tuberculosis. Streptococcus pyogenes is known for causing strep throat and skin infections, Escherichia coli is commonly involved in gastrointestinal infections, and Bacillus anthracis causes anthrax.

Correct Answer: A

Rationale: The correct answer is A: Salmonella enterica. This is because Salmonella are Gram-negative rods that do not ferment lactose, which fits the description in the question. Additionally, Salmonella is a common cause of severe abdominal pain and diarrhea. Shigella dysenteriae is a Gram-negative rod that also causes severe diarrhea but it does not share the characteristic of not fermenting lactose. Escherichia coli is a Gram-negative rod that does ferment lactose. Proteus vulgaris is also a Gram-negative rod but it is not commonly associated with severe abdominal pain and diarrhea, making it an unlikely causative agent in this scenario.

Correct Answer: A

Rationale: The correct answer is A because Legionellae are typically found in natural water sources such as lakes, rivers, and soil. Legionellae thrive in aquatic environments and can also be present in mud. Choice B is incorrect as Legionellae are not limited to infected humans but are also found in the natural environment. Choice C is incorrect as Legionellae are not primarily associated with infected animals. Choice D is incorrect as Legionellae do have natural reservoirs in water and soil.

Correct Answer: C

Rationale: Rationale: 1. The presence of ulcers in animals suggests a parasitic infection. 2. Mosquitoes as carriers indicate a protozoan transmitted through insect bites. 3. Among the choices, Plasmodium falciparum causes malaria transmitted by mosquitoes. 4. Leishmania tropica major causes cutaneous leishmaniasis, not ulcers. 5. Balantidium coli causes intestinal infections, not skin ulcers. 6. Trypanosoma cruzi causes Chagas disease, not skin ulcers.

Correct Answer: B

Rationale: The correct answer is B: Gram's staining method. The rationale for this is as follows: Gentian violet and Lugol's solution are used as primary and mordant stains in the Gram's staining method. Spiritus 960 is used as a decolorizer, and water fuchsin is used as a counterstain. This staining method is commonly used in microbiology to differentiate bacteria into Gram-positive and Gram-negative based on their cell wall characteristics. A: Leffler's staining method is used for the identification of diphtheria bacilli. C: Ziehl-Neelsen's staining method is used for acid-fast bacteria like Mycobacterium tuberculosis. D: Neisser's staining method is used for the identification of Neisseria species. In summary, the use of specific reactives and stainers in the question indicates the application of the Gram's staining method for bacterial differentiation.