microbiology an evolving science test bank

Correct Answer: A

Rationale: The correct answer is A: ethylene oxide. Ethylene oxide is a toxic, odorless gas commonly used as a sterilizing agent in healthcare settings due to its ability to effectively kill bacteria, viruses, and fungi. It is a highly reactive compound that can penetrate porous materials, making it an ideal choice for sterilization purposes. Incorrect choices: B: Carbon dioxide is not used as a sterilizing agent and is not toxic. C: Carbon monoxide is not commonly used for sterilization and has a distinct odor. D: Propane is not used for sterilization in healthcare settings and is not odorless.

Correct Answer: D

Rationale: The correct answer is D because all three bacteria (Salmonella enterica, Escherichia coli, Pseudomonas aeruginosa) are known to produce endotoxins, specifically lipopolysaccharides in their cell walls. Endotoxins are released upon bacterial cell death and can trigger an immune response, leading to septic shock. Salmonella and E. coli are common causes of bacterial infections, while Pseudomonas is associated with nosocomial infections. Therefore, all of the above choices are correct in terms of producing endotoxins that can cause septic shock. Choices A, B, and C are incorrect individually because they do not encompass all the bacteria known to produce endotoxins that can lead to septic shock.

Correct Answer: C

Rationale: The correct answer is C: Tuberculosis. Granulomas with lymphocytes and macrophages containing Virchow's cells (large cells with fat inclusions containing microorganisms) are classic findings in tuberculosis. Leprosy (A) typically presents with granulomas but with different histopathological features. Syphilis (B) does not usually form granulomas in the skin. Rhinoscleroma (D) is a chronic bacterial infection characterized by nodular lesions but does not typically involve Virchow's cells as seen in tuberculosis.

Correct Answer: B

Rationale: The correct answer is B: Penicillin. Penicillin is the drug of first choice for treating syphilis due to its effectiveness in eradicating the bacterium Treponema pallidum, which causes syphilis. It is the most reliable treatment with well-established efficacy. Gentamicin (A), ciprofloxacin (C), and chloramphenicol (D) are not recommended for treating syphilis as they are not effective against the specific bacteria causing the infection. Penicillin remains the gold standard for syphilis treatment.

Correct Answer: B

Rationale: Step-by-step rationale for why B (Gamma Interferon) is the correct answer: 1. Gamma Interferon is a type of immunomodulator that helps regulate the immune response. 2. It activates macrophages and enhances the immune system's ability to fight infections. 3. Rifampin is an antibiotic, not an immunomodulator. 4. Hexacima and Pentaxim are combination vaccines, not immunomodulators. In summary, Gamma Interferon is the correct answer as it directly influences the immune response, while the other choices are not immunomodulators.