Which of the following antibiotics is primarily used to treat Gram-negative bacterial infections?

Aminoglycosides are primarily used to treat Gram-negative bacterial infections due to their effectiveness against aerobic Gram-negative bacteria. This class of antibiotics works by inhibiting protein synthesis in bacteria, which is crucial for their growth and reproduction. Drugs such as gentamicin and tobramycin belong to this category and are often utilized in clinical settings for serious infections caused by Gram-negative organisms, including Pseudomonas aeruginosa and Escherichia coli.

In contrast, other classes of antibiotics listed may have a broader spectrum of activity but are not specifically targeted at Gram-negative bacteria. For example, vancomycin is primarily effective against Gram-positive organisms, making it unsuitable for treating infections caused by Gram-negative bacteria. Cephalosporins and tetracyclines can also target a range of Gram-positive and some Gram-negative bacteria, but the effectiveness of aminoglycosides against particularly resistant Gram-negative strains makes them a preferred choice in specific cases. Thus, aminoglycosides are essential in managing infections where Gram-negative coverage is crucial.