Microbiology Chapter 11 Test Bank

Correct Answer: A

Rationale: The correct answer is A: Contaminated. The air is never completely free of microorganisms, so it is considered contaminated. Microorganisms are ubiquitous in the environment. Permissible limits (B) imply a specific standard, which is not relevant to the general microbiological characteristic of air. Almost pure (C) and pure (D) are not accurate as air always contains some level of microorganisms.

Correct Answer: A

Rationale: Step-by-step rationale: 1. Mumps is a contagious disease transmitted through air droplets and direct contact. 2. The correct answer is A because mumps can infect both humans and animals. 3. Choice B is incorrect as mumps is vaccine-preventable. 4. Choice C is correct as mumps is highly contagious. 5. Choice D is accurate as mumps is transmitted via air droplets and direct contact. Summary: The correct answer is A because mumps can infect both humans and animals, making it untrue that only humans can be infected. Choices B, C, and D are incorrect as mumps is vaccine-preventable, highly contagious, and transmitted through air droplets and direct contact.

Correct Answer: D

Rationale: The correct answer is D: IgM. IgM antibodies are the first type of antibodies produced by the immune system in response to an acute infection, such as Parvovirus B19. During the first 10-14 days of the infection, IgM antibodies are usually detectable in the blood, indicating a recent or ongoing infection. IgG antibodies (choice A) are produced later in the immune response and indicate past infection or immunity. IgA (choice B) is more commonly associated with mucosal immunity and may not be as prominent in the early stages of systemic infections. IgD (choice C) is primarily found on the surface of B cells and is involved in B cell activation but is not typically used as a marker for acute infections like IgM.

Correct Answer: A

Rationale: The correct answer is A: Entamoeba histolytica. This is because it is the only choice that matches the description of cysts with four nuclei, characteristic of Entamoeba histolytica. Entamoeba histolytica is a protozoan parasite that causes amoebiasis, leading to symptoms like persistent diarrhea. The other choices can be eliminated for the following reasons: B: Balantidium coli - It is a ciliated protozoan that causes dysentery in humans but does not produce cysts with four nuclei. C: Giardia lamblia - It is a flagellated protozoan that causes giardiasis, but it forms cysts with only two nuclei. D: Trichomonas hominis - It is a flagellated protozoan found in the human intestine, but it does not produce cysts with four nuclei. Therefore, based on the description of cysts with four nuclei in the stool sample,

Correct Answer: D

Rationale: The correct answer is D: Middlebrook's medium. This medium is specifically designed for the growth of Mycobacterium tuberculosis due to its low concentration of malachite green, which inhibits the growth of other bacteria but not Mycobacterium species. Middlebrook's medium also contains various nutrients that support the growth of Mycobacterium tuberculosis. A: Middlebrook's medium is the correct answer, not incorrect. B: Heart infusion broth is a general-purpose medium, not specific for Mycobacterium tuberculosis. C: MacConkey agar is selective for gram-negative bacteria and would not support the growth of Mycobacterium tuberculosis. In summary, Middlebrook's medium is the ideal choice for cultivating Mycobacterium tuberculosis due to its specific formulation that promotes the growth of this pathogen while inhibiting other bacteria.