microbiology chapter 11 test bank

Correct Answer: A

Rationale: The correct answer is A: HIV. HIV is an example of obligate parasitism because it requires a host cell to replicate and survive. It cannot live independently outside of a host organism. In contrast, choices B, C, and D are not obligate parasites. E. Coli and S. Epidermidis are examples of commensal bacteria that can live in the host without causing harm. Pseudomonas aeruginosa can be both an opportunistic pathogen and a free-living organism, not strictly dependent on a host for survival.

Correct Answer: B

Rationale: The correct answer is B, Helicobacter pylori. This bacterium is the main cause of peptic ulcers by damaging the protective lining of the stomach and duodenum. It secretes enzymes that weaken the mucosal barrier, allowing stomach acid to cause damage. Salmonella typhi (A) causes typhoid fever, not peptic ulcers. Shigella boydii (C) causes dysentery, not peptic ulcers. Salmonella enterica (D) causes food poisoning, not peptic ulcers. Therefore, the correct answer is B based on its direct association with peptic ulcer formation.

Correct Answer: B

Rationale: The correct answer is B: Absence of hemagglutination. In the reaction inhibition of hemagglutination, specific antibodies bind to antigens on red blood cells, preventing their agglutination. This results in the absence of visible clumping of red blood cells, which is known as hemagglutination. Therefore, the presence of specific antibodies is visualized by the absence of hemagglutination. Incorrect Choices: A: Absence of hemolysis - Hemolysis refers to the rupture of red blood cells, which is not relevant in the context of hemagglutination. C: Presence of hemagglutination - This is the opposite of what is expected when specific antibodies are present and inhibiting hemagglutination. D: Presence of hemolysis - Again, hemolysis is not directly related to the inhibition of hemagglutination by specific antibodies.

Correct Answer: D

Rationale: Conjugation involves direct cell-to-cell contact for the transfer of genetic material, typically through a pilus. This process is well-documented in bacterial genetics. Transformation (A) involves uptake of free DNA from the environment. Transduction (B) is genetic transfer by a viral vector. Replication (C) is the process of producing identical copies of DNA or RNA. Therefore, the correct answer is D (conjugation) as it specifically refers to the one-way transfer of genetic material through direct cell-to-cell contact.

Correct Answer: A

Rationale: The correct answer is A: IgG. Anti-tetanus gamma globulin is produced by hyperimmunization, leading to a high concentration of specific antibodies, predominantly IgG. IgG is the most abundant immunoglobulin in the blood and provides long-term immunity against tetanus. IgA is mainly found in mucosal areas, not in gamma globulin preparations. IgM is the first antibody produced in response to an infection and is not the prevailing class in this preparation. IgE is associated with allergic reactions and parasitic infections, not with anti-tetanus immunity.