The highest incidence of antibiotic associated pseudomembranous enterocolitis has been noted with the use of:

Correct Answer: D

Rationale: The correct answer is D: Clindamycin. Clindamycin is associated with the highest incidence of antibiotic-associated pseudomembranous enterocolitis due to its broad-spectrum activity that disrupts the normal gut flora, leading to overgrowth of Clostridium difficile. Ampicillin, Chloramphenicol, and Vancomycin are also associated with pseudomembranous enterocolitis, but the highest incidence is seen with Clindamycin due to its stronger impact on gut flora imbalance.

Correct Answer: B

Rationale: The correct answer is B: Ciprofloxacin. Ciprofloxacin is a fluoroquinolone antibiotic that interferes with DNA function in bacteria by inhibiting DNA gyrase and topoisomerase IV enzymes. This mechanism of action prevents bacterial DNA replication and repair, leading to bacterial cell death. Ciprofloxacin is effective in treating gonorrhea due to its ability to target and kill Neisseria gonorrhoeae, the bacteria causing gonorrhea. A: Chloramphenicol inhibits bacterial protein synthesis, not DNA function. C: Streptomycin disrupts bacterial protein synthesis by binding to the ribosome, not DNA function. D: Erythromycin inhibits bacterial protein synthesis by binding to the ribosome, not DNA function.

Correct Answer: zidovudine diphosphate

Rationale: The correct answer is D: Zidovudine is converted by cellular enzymes to an active form (zidovudine diphosphate). Zidovudine itself is a prodrug that needs to be metabolized by cellular enzymes to its active form, zidovudine diphosphate, which inhibits HIV replication by acting as a nucleoside reverse transcriptase inhibitor. This active form is essential for its antiretroviral activity. Incorrect Choices: A: Zidovudine in combination with other antiretrovirals is an alternative initial treatment for HIV infection - This is incorrect because zidovudine is commonly used in combination with other antiretrovirals as a first-line treatment for HIV infection, not as an alternative treatment. B: Zidovudine is also used to prevent transmission of HIV from the mother to her fetus and to treat AIDS-related dementia - This is incorrect because zidovudine is primarily used in

Correct Answer: B

Rationale: The correct answer is B: Crotamiton. Crotamiton is not a topical antifungal drug; it is a scabicidal and antipruritic agent used to treat scabies and itching. Tolnaftate (A), Terbinafine (C), and Ciclopirox (D) are all topical antifungal drugs used to treat various fungal skin infections. Tolnaftate is commonly used for athlete's foot, ringworm, and jock itch. Terbinafine is effective against fungal infections like athlete's foot and ringworm. Ciclopirox is used to treat fungal infections like athlete's foot and ringworm as well.

Correct Answer: B

Rationale: The correct answer is B: Amoxicillin. This penicillin has an extended spectrum of activity against gram-negative bacilli, making it effective against a wider range of bacteria. It is acid-resistant, allowing it to be taken orally, but it is not penicillinase-resistant, meaning it can be easily degraded by beta-lactamase enzymes. A: Cloxacillin is penicillinase-resistant but does not have an extended spectrum against gram-negative bacilli. C: Phenoxymethyl penicillin is not acid-resistant and does not have an extended spectrum against gram-negative bacilli. D: Piperacillin has an extended spectrum of activity but is not acid-resistant and is susceptible to penicillinase.