Which of the following is NOT a bactericidal agent?

Tetracycline is not classified as a bactericidal agent; rather, it is considered a bacteriostatic antibiotic. Bacteriostatic antibiotics work by inhibiting bacterial growth and reproduction without directly killing the bacteria. Tetracycline achieves this by binding to the bacterial ribosome, thereby interfering with protein synthesis. This inhibition prevents the bacteria from growing and multiplying, allowing the immune system to eliminate the infection.

In contrast, the other options mentioned—penicillin, cephalosporin, and vancomycin—are all bactericidal agents. They work by directly killing bacteria. For instance, penicillin and cephalosporins disrupt bacterial cell wall synthesis, leading to cell lysis. Vancomycin also targets the bacterial cell wall but is particularly effective against gram-positive bacteria.

Understanding the distinction between bactericidal and bacteriostatic agents is crucial in pharmacology, especially when considering treatment strategies and the types of infections being addressed.