Which of the following cephalosporins has activity against gram negative anaerobic bacteria like Bacteroides fragilis, and the only cephalosporins that cross the blood brain barrier and enter the brain?

Correct Answer: A

Rationale: Rationale: 1. Ceftriaxone is a third-generation cephalosporin known for broad-spectrum coverage. 2. It has excellent activity against gram-negative anaerobes such as Bacteroides fragilis. 3. It is also one of the cephalosporins that can penetrate the blood-brain barrier. 4. The other choices do not have the same anaerobic coverage or BBB penetration. Summary: - B: Cefoxitin is a second-generation cephalosporin with anaerobic coverage but does not cross the BBB. - C: Cephalexin is a first-generation cephalosporin with limited anaerobic activity and no BBB penetration. - D: Cefixime is a third-generation cephalosporin with no anaerobic activity or BBB penetration.

Correct Answer: A

Rationale: The correct answer is A: Zidovudine. Zidovudine is known to cause bone marrow suppression, leading to decreased white blood cell and red blood cell counts. In this case, the patient's peripheral WBC count of 1000 and low hemoglobin after starting therapy are indicative of hematologic abnormalities consistent with zidovudine use. Acyclovir, Foscarnet, and Amantadine do not typically cause bone marrow suppression and are not associated with the hematologic abnormalities seen in this patient.

Correct Answer: A

Rationale: Rationale: 1. Ganciclovir is the preferred antiviral for CMV infections due to its effectiveness against CMV. 2. It works by inhibiting viral DNA polymerase, stopping viral replication. 3. Indinavir is a protease inhibitor used for HIV, not CMV. 4. Amantadine is used for influenza A virus, not CMV. 5. Foscarnet is an alternative for CMV if ganciclovir is not tolerated.

Correct Answer: A

Rationale: The correct answer is A: Benzathine penicillin. Benzathine penicillin has the longest duration of action among the choices because it is formulated as a salt that releases the active drug slowly over an extended period. The benzathine salt forms a depot at the injection site, leading to a sustained release of penicillin into the bloodstream. This results in a prolonged therapeutic effect and less frequent dosing compared to other penicillin preparations. Summary: - Choice B: Sodium penicillin has a shorter duration of action as it gets rapidly absorbed and eliminated from the body. - Choice C: Potassium penicillin is not a standard form of penicillin and does not exist as a distinct preparation. - Choice D: Procaine penicillin has an intermediate duration of action compared to benzathine penicillin due to the addition of procaine for local anesthesia, but it is not as long-acting.

Correct Answer: D

Rationale: The correct answer is D because both statements (A and B) are accurate. A: Metronidazole is a first-line drug for amoebic dysentery and liver abscess due to its efficacy against Entamoeba histolytica. B: Metronidazole is a prodrug that gets activated to form nitro intermediates, which bind DNA and disrupt anaerobic microbial replication. Therefore, option D is correct as both A and B provide accurate information about metronidazole. Option C is incorrect as metronidazole is not specifically targeted to eradicating amoebic cysts from the colon.