microbiology chapter 13 test bank

Correct Answer: C

Rationale: Rationale: C is the correct answer because antibodies formed against Mycobacterium tuberculosis are not protective. They do not efficiently clear the infection due to the bacterium's ability to evade the immune response by residing intracellularly in macrophages. Antibodies play a minimal role in controlling tuberculosis compared to cell-mediated immunity. Summary: A is incorrect because Mycobacterium tuberculosis does contain mycolic acid in its cell wall. B is incorrect because the pathogen can indeed live intracellularly in macrophages. D is incorrect as C is the correct answer.

Correct Answer: C

Rationale: The correct answer is C: Method of Moller. This method uses malachite green to stain bacterial spores due to their resistance to decolorization. The other choices, A, B, and D, are incorrect because Romanovski-Gymsa is used for staining blood smears, Ziehl-Nielsen is used for acid-fast bacteria, and Neisser is used for staining Neisseria species, not bacterial spores.

Correct Answer: D

Rationale: The correct answer is D: Relapsing fever. The description matches Borrelia species, the causative agent of relapsing fever. The thin, spiral-shaped microorganisms with pointed ends and specific length are characteristic of Borrelia. The number of coils and size mentioned also align with Borrelia morphology. Relapsing fever is transmitted by tick bites and manifests as recurring febrile episodes. Incorrect choices: A: Syphilis - Syphilis is caused by Treponema pallidum, which is not spiral-shaped. B: Trypanosomiasis - Trypanosomiasis is caused by Trypanosoma species, which are not spiral-shaped. C: Leptospirosis - Leptospirosis is caused by Leptospira species, which are not spiral-shaped and do not match the specific description provided.

Correct Answer: A

Rationale: The correct answer is A: Neisser staining method. Neisser staining method is used to stain diphtheria bacilli, which appear as blue rods with thickenings at the poles. The rationale is that Neisser staining specifically targets and highlights the characteristics of the diphtheria bacilli. Incorrect choices: B: Gram staining is not specific for diphtheria bacilli and does not show the characteristic blue rods with thickenings at the poles. C: Ziehl-Neelsen staining is used for acid-fast bacteria like Mycobacterium tuberculosis, not for diphtheria bacilli. D: Loeffler staining is used for diphtheria bacilli but does not produce blue rods with thickenings at the poles as seen in this case.

Correct Answer: A

Rationale: The correct answer is A because spirochaetes are not bacilli; they are spiral-shaped bacteria. Bacilli are rod-shaped bacteria, making statement A false. Statement B is true as diplococci are spherical bacteria occurring in pairs. Statement C is true as rod-shaped bacteria have one diameter longer than the other. Statement D is true as coccobacilli are short, oval-shaped bacteria resembling cocci and rods. In summary, spirochaetes are spiral-shaped, not bacilli, making statement A false.