Primarily used in the treatment of Gram-negative infections such as UTIs.

• A. Cefazolin
• B. Amikacin
• C. Vancomycin
• D. Gentamicin

Answer: (D)

Aminoglycosides are bactericidal antibiotics that bind the 30S ribosomal subunit, causing misreading of mRNA and a halt in protein synthesis. They work best against aerobic Gram-negative bacilli, making them a mainstay for Gram-negative infections such as urinary tract infections, often used in combination with beta-lactams for synergistic effect.

Gentamicin fits this use pattern perfectly. It has strong activity against Enterobacteriaceae and Pseudomonas, which are common Gram-negative culprits in UTIs. It is not effective against most Gram-positive organisms and has limited anaerobic activity, so it’s not the choice for infections caused by those bacteria.

Cefazolin targets mostly Gram-positive cocci with limited Gram-negative coverage, so it’s not the drug of choice for typical Gram-negative UTIs. Vancomycin is reserved for Gram-positive infections. Amikacin is another aminoglycoside with broad Gram-negative activity and is used in some resistant infections, but Gentamicin is the classic agent most commonly associated with treating Gram-negative infections such as UTIs.