microbiology an evolving science test bank

Correct Answer: B

Rationale: The correct answer is B: microaerophiles. These bacteria require oxygen to grow, but only at low concentrations as higher levels can be toxic. They possess enzymes to deal with reactive oxygen species. Obligate aerobes (A) require oxygen for growth, obligate anaerobes (C) cannot survive in the presence of oxygen, and aerotolerant anaerobes (D) can tolerate oxygen but do not use it for growth.

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.

Correct Answer: A

Rationale: The correct answer is A: Actinomycosis. This is a chronic bacterial infection caused by Actinomyces species. In this case, the description of dense yellow-green colored focus, white granules in purulent masses, and presence of fungal druses, plasma cells, xanthome cells, and macrophages all match the characteristics of actinomycosis. Actinomycosis typically presents with abscess formation containing sulfur granules, which are yellowish and granular. The other choices (B: Furuncle, C: Carbuncle, D: Syphilis) do not fit the clinical and histological features described in the question, making them incorrect options.

Correct Answer: C

Rationale: The correct answer is C: E + S = P. This notation represents the interaction between an enzyme (E) and a substrate (S) resulting in a product (P). Enzymes facilitate chemical reactions by binding to substrates and converting them into products. Choice A is incorrect because it does not include the enzyme in the reaction. Choice B is incorrect as it involves two substrates binding to the enzyme, not a substrate converting to a product. Choice D is incorrect as it shows two substrates reacting to form a product without involvement of an enzyme. Thus, choice C accurately represents the process of enzymatic reactions involving enzymes, substrates, and products.

Correct Answer: C

Rationale: Plasmids often carry antibiotic resistance genes, making choice C correct. Plasmids are circular DNA structures, not linear (A). They are found in both gram-positive and gram-negative bacteria, not exclusively in gram-positive bacteria (B). Plasmids are separate from the bacterial chromosome, not part of it (D). Therefore, choice C is the correct answer.