microbiology chapter 12 test bank

Correct Answer: D

Rationale: The correct answer is D: peroxisomes. Peroxisomes contain oxidative enzymes, such as catalase and peroxidase, that are capable of oxidizing toxic substances. These enzymes help detoxify harmful molecules by breaking them down into harmless products. Lysosomes (choices B and C) contain hydrolytic enzymes for breaking down cellular waste, not oxidative enzymes. Therefore, the correct choice is peroxisomes due to their specific function in detoxification through oxidation reactions.

Correct Answer: A

Rationale: The correct answer is A: Vibrio cholerae. Vibrio cholerae is the causative agent of cholera, which presents with severe watery diarrhea leading to dehydration. The characteristic comma-shaped (curved rod) appearance of Gram-negative bacteria is typical of Vibrio cholerae. This bacterium produces the cholera toxin, leading to the excessive secretion of fluid into the intestines. Salmonella typhi causes typhoid fever with symptoms like sustained fever, not watery diarrhea. Shigella dysenteriae causes bloody diarrhea and abdominal cramps. Escherichia coli can cause various types of infections, but typically not severe watery diarrhea like cholera.

Correct Answer: A

Rationale: The correct answer is A: Bacterial endospores. Bacterial endospores have a higher resistance to environmental stresses due to their unique structure, which includes a tough outer layer that protects the spore from harsh conditions such as heat, chemicals, and radiation. This protective layer allows endospores to remain dormant and survive in unfavorable environments until conditions improve. Summary: B: Fungal spores - While fungal spores can also survive in harsh conditions, they are generally not as resistant as bacterial endospores due to differences in their protective structures. C: Enveloped viruses - Enveloped viruses are susceptible to environmental stresses as their lipid envelope can easily be damaged by heat, chemicals, and other factors. D: Vegetative bacterial cells - Vegetative bacterial cells are more susceptible to environmental stresses compared to endospores, as they do not have the same level of protective mechanisms to survive in unfavorable conditions.

Correct Answer: A

Rationale: The correct answer is A: Syphilitic granulomas (gummas). In the tertiary stage of syphilis, gummas, which are soft, tumor-like growths, can develop in various organs such as the skin, bones, liver, and brain. This stage typically occurs years after the initial infection and can lead to serious complications if left untreated. Purulent exudation from the urethra (B) is not specific to syphilis and may indicate other infections. Non-tender chancre (C) is characteristic of the primary stage of syphilis, not the tertiary stage. Diffuse maculopapular rash (D) is more commonly seen in the secondary stage of syphilis.

Correct Answer: A

Rationale: The likely diagnosis is Meningococcal meningitis (Choice A) due to the presence of Gram-negative diplococci in the cerebrospinal fluid. Neisseria meningitidis is a Gram-negative diplococcus commonly associated with meningococcal meningitis. Fever, chills, and neck stiffness are classic symptoms of bacterial meningitis, and Neisseria meningitidis often presents with these symptoms. Pneumococcal meningitis (Choice B) is caused by Streptococcus pneumoniae, a Gram-positive organism. Haemophilus influenzae (Choice C) is also a Gram-negative organism but typically presents with a different clinical picture. Listeria monocytogenes (Choice D) is a Gram-positive rod and is more commonly associated with meningitis in neonates, elderly, and immunocompromised individuals.