Which antibiotic is primarily bacteriostatic but becomes bactericidal at higher * concentrations?:

Correct Answer: C

Rationale: The correct answer is C: Chloramphenicol. At lower concentrations, Chloramphenicol is primarily bacteriostatic, inhibiting bacterial protein synthesis. However, at higher concentrations, it can disrupt the bacterial ribosome, leading to bacterial cell death, making it bactericidal. Erythromycin (A) and Tetracycline (B) are primarily bacteriostatic by inhibiting protein synthesis. Ampicillin (D) interferes with bacterial cell wall synthesis but does not exhibit a concentration-dependent shift to bactericidal activity like Chloramphenicol.

Correct Answer: B

Rationale: The correct answer is B: Acetazolamide. Acetazolamide is a carbonic anhydrase inhibitor that can worsen hyperuricemia by increasing renal uric acid reabsorption. This can further exacerbate the risk of acute uric acid nephropathy. Ethacrynic acid (A), Hydrochlorothiazide (C), and Furosemide (D) are loop diuretics that can actually help in reducing uric acid levels by increasing its excretion through the urine. Therefore, they would not be contraindicated in this scenario.

Correct Answer: C

Rationale: The correct answer is C: Gentamycin. Gentamycin is not recommended in this case due to its potential for nephrotoxicity, especially in patients already receiving furosemide. Furosemide is a loop diuretic that can also cause kidney damage, so combining it with Gentamycin increases the risk of further renal impairment. Cotrimoxazole (A) and Ampicillin (D) are commonly used antibiotics that do not have significant interactions with furosemide and Digoxin. Ciprofloxacin (B) is a fluoroquinolone antibiotic that is generally safe to use in patients with CHF and UTI.

Correct Answer:

Rationale: The correct answer is A: renal pelvis. The renal pelvis is not directly related to the action of antidiuretic hormone (ADH) in the nephron. ADH regulates water reabsorption in the collecting duct of the nephron to maintain water balance in the body. Choices B, C, and D are incorrect because they are all associated with the function of ADH in the nephron. ADH regulates the amount of water reabsorbed in the distal tubule and collecting duct, not the renal pelvis.

Correct Answer: B

Rationale: The correct answer is B because a positive dipstick for leucocyte esterase is not 96% specific for >10 wbc/mm³. Leucocyte esterase can indicate the presence of white blood cells, but it does not quantitatively correlate with a specific wbc count. Therefore, it cannot be used to accurately determine the exact wbc count in the urine sample. A: The sensitivity of dipstick for nitrites being 96% means it is good at detecting nitrites, which are a sign of bacterial infection in the urine. C: A bacterial culture with >10^5 colony-forming units has a high probability of representing infection, typically around 95%. D: Blood cultures are not routinely used for diagnosing UTIs; urine culture is the primary method. Blood cultures are more often used for systemic infections.