Microbiology An Introduction 12th Edition Test Bank

Correct Answer: C

Rationale: The correct answer is C: Quinine. Quinine is known for its destructive effect on erythrocytic forms of malarial plasmodia and dysenteric amoebae. It is commonly used for the treatment and prevention of diseases such as malaria, amebiasis, and interstitial disease. Quinine works by interfering with the parasite's ability to break down hemoglobin in red blood cells, ultimately leading to their destruction. Incorrect choices: A: Chingamin - Chingamin is not typically used to treat malaria, amebiasis, or interstitial disease. B: Emetine hydrochloride - Emetine hydrochloride is primarily used for treating amoebic dysentery and is not commonly used for malaria treatment. D: Erythromycin - Erythromycin is an antibiotic used to treat bacterial infections, not parasitic infections like malaria or amebiasis.

Correct Answer: A

Rationale: The correct answer is A: Gp120. Gp120 is a glycoprotein on the surface of the HIV virus that specifically binds to the CD4 receptor on target cells. This binding is essential for the virus to enter the host cell and initiate the infection process. Gp41 is another glycoprotein on the virus that helps with membrane fusion, not binding to CD4. Gp32 and Gp55 are not involved in the specific binding of HIV to CD4 molecules. So, A is correct as it directly plays a key role in the initial attachment of HIV to target cells.

Correct Answer: A

Rationale: The correct answer is A: Staphylococcus epidermidis. 1. Gram-positive cocci suggest a staphylococcal species. 2. Catalase-positive indicates it belongs to the Staphylococcus genus. 3. Coagulase-negative rules out Staphylococcus aureus. 4. Staphylococcus epidermidis is a common cause of infections in immunocompromised patients. Summary: - B: Staphylococcus aureus is coagulase-positive. - C: Streptococcus pneumoniae is a Gram-positive diplococci. - D: Neisseria meningitidis is a Gram-negative diplococci.

Correct Answer: B

Rationale: The correct answer is B: prophage. In the repressed stage, a phage integrates its DNA into the host cell's chromosome, becoming a prophage. This integration allows the phage to replicate along with the host cell without causing immediate lysis. A: Antiphage is not a term used to describe a phage in a repressed stage. C: Virulent phage refers to a phage that immediately causes lysis of the host cell. D: Latent phage is not a commonly used term in this context.

Correct Answer: A

Rationale: The correct answer is A because a soft chancre is a type of sexually transmitted infection caused by the bacterium Haemophilus ducreyi. It presents as a painless ulcer on the genitals. The other choices are incorrect. B is incorrect because STIs can enter the body through various routes, not only the urogenital tract mucosa. C is incorrect because immunity to syphilis is not lifelong; reinfection is possible. D is incorrect because STIs can occur in any country regardless of social status or hygiene levels.