openstax microbiology test bank

Correct Answer: A

Rationale: The correct answer is A: The polysaccharide capsule. The capsule of Neisseria meningitidis plays a crucial role in its virulence by preventing phagocytosis, allowing the bacteria to evade the host's immune system. This leads to increased survival and colonization in the host. Choice B: The beta lactamase is incorrect because it is an enzyme that breaks down beta-lactam antibiotics and does not directly contribute to the virulence of Neisseria meningitidis. Choice C: The erythrogenic toxin is incorrect as this toxin is produced by Streptococcus pyogenes, not Neisseria meningitidis. Choice D: None of the above is incorrect as the polysaccharide capsule is indeed a key virulence factor of Neisseria meningitidis.

Correct Answer: C

Rationale: The correct answer is C: genes with plasmid location. Clostridium tetani produces exotoxins through genes located on plasmids. Plasmids are extrachromosomal genetic elements that carry additional genes. These genes encode for the production of exotoxins in Clostridium tetani. Choices A, B, and D are incorrect because Clostridium tetani does produce exotoxins, it does not have only endotoxin activity, and the genes responsible for exotoxin production are located on plasmids, not solely on the chromosome or both chromosome and plasmid.

Correct Answer: C

Rationale: The correct answer is C: ELISA, Western blot. These tests are commonly used for diagnosing Lyme borreliosis due to their high sensitivity and specificity in detecting antibodies against Borrelia burgdorferi, the causative agent. ELISA is the initial screening test, while Western blot is used for confirmation. Widal agglutination test (A) is used for diagnosing typhoid fever, not Lyme disease. Cultivation on blood and chocolate agar (B) is not commonly used for diagnosing Lyme borreliosis as Borrelia species are difficult to culture. Ascoli thermoprecipitation test (D) is used for diagnosing pneumonia caused by Streptococcus pneumoniae, not Lyme disease.

Correct Answer: A

Rationale: The correct answer is A: Peptidoglycan. Bacterial cell walls are composed of peptidoglycan, a unique macromolecule consisting of sugars and amino acids. This structure provides rigidity and protection to the cell. Lipopolysaccharides are found in the outer membrane of Gram-negative bacteria, not in the cell wall. Phospholipids are the main components of cell membranes, not cell walls. Chitin is a structural polysaccharide found in the cell walls of fungi and some algae, not bacteria.

Correct Answer: B

Rationale: The Ziehl-Neelsen stain is specifically designed to detect acid-fast bacteria like Mycobacterium tuberculosis. It utilizes a carbol fuchsin dye that binds to the high lipid content in the cell wall of acid-fast bacteria, making them appear red under a microscope. This staining method is crucial for the diagnosis of tuberculosis and leprosy. Gram-positive bacteria (Choice A) are not detected by this stain since they have a different cell wall structure. Capsulated bacteria (Choice C) and fungal spores (Choice D) also have distinct characteristics that are not targeted by the Ziehl-Neelsen stain.