microbiology chapter 11 test bank

Correct Answer: B

Rationale: Rationale: 1. Enteropathogenic E.coli (EPEC) adheres to the intestinal wall using bundle-forming pili. 2. EPEC produces toxins that disrupt cell structure and function, leading to diarrhea. 3. Shigella spp. invade intestinal cells, Salmonella spp. invade and multiply within cells, and Vibrio cholerae produces cholera toxin causing profuse watery diarrhea. Summary: A, C, and D choices are incorrect because they do not specifically adhere to the intestine wall and produce toxins like EPEC does.

Correct Answer: C

Rationale: Legionella pneumophila is a Gram-negative coccobacillus. It is not a coccus (round shape), spiral bacterium, or Gram-positive coccobacillus. The correct answer is C because Legionella pneumophila has a characteristic coccobacillary shape and stains Gram-negative due to its cell wall composition. The other choices are incorrect because they do not accurately describe the morphology or staining characteristics of Legionella pneumophila.

Correct Answer: A

Rationale: Axial filaments, also known as endoflagella, are composed of proteins. These proteins form a helical structure that enables certain bacteria, such as spirochetes, to move in a corkscrew-like motion. Proteins are the main structural component of axial filaments due to their flexibility and ability to generate movement. Choice B, polyphosphates, are not typically associated with axial filaments, as they are more involved in energy storage and transfer. Choice C, volutin granules, are storage inclusions of inorganic polyphosphate and are not part of axial filaments. Choice D, carbohydrates, are not the primary component of axial filaments which are protein-based structures responsible for bacterial motility.

Correct Answer: A

Rationale: Rationale: - Yersinia enterocolitica is a common cause of diarrhea due to contaminated food or water. - It typically presents with symptoms such as abdominal pain, fever, and diarrhea. - The other choices are unlikely causes of prolonged diarrhea, as Bordetella pertussis causes whooping cough, Neisseria meningitidis causes meningitis, and Corynebacterium diphtheria causes diphtheria.

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,