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: A

Rationale: The correct answer is A: Bordetella pertussis. Glossy smooth colonies growing on casein-charcoal agar resembling mercury drops indicate Bordetella pertussis, the causative agent of whooping cough. The presence of short Gram-negative bacteria further supports this identification. Option B, Haemophilus influenzae, typically grows as small, round, translucent colonies on chocolate agar. Option C, Corynebacterium diphtheriae, forms gray colonies on tellurite agar. Option D, Klebsiella pneumoniae, appears as mucoid colonies on MacConkey agar.

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: Rationale: 1. Spore-forming, Gram-positive rods: Characteristics shared by Clostridium and Bacillus. 2. Motile and gas production in nutrient broth: Clostridium perfringens is motile and produces gas, distinguishing it from Bacillus species. 3. Clostridium perfringens causes gas gangrene, correlating with gas production. 4. Bacillus anthracis causes anthrax, not related to wound infections. 5. Clostridium tetani causes tetanus, not associated with gas production. 6. Bacillus cereus causes food poisoning, not commonly associated with wound infections. Summary: - A is correct (Clostridium perfringens) due to motility, gas production, and wound infection correlation. - B (Bacillus anthracis) causes anthrax, not wound infections. - C (Clostridium tetani) causes tetanus, not gas production. - D (B

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.