Antimicrobial Therapy Practice Test

Binding to the 50S ribosomal subunit with a bacteriostatic effect and a very broad spectrum that includes Rickettsia, Haemophilus influenzae, Neisseria meningitidis, and Bacteroides is the profile of chloramphenicol. It works by inhibiting the peptidyl transferase activity on the 50S subunit, halting protein synthesis and preventing bacterial growth. This combination of mechanism and coverage fits chloramphenicol precisely, since other options act differently or have different coverage: tetracycline blocks the 30S subunit; erythromycin (a macrolide) binds the 50S but does not reliably cover Bacteroides and has variable activity against some organisms on the list; clindamycin targets the 50S and is great for anaerobes like Bacteroides but doesn’t cover Rickettsia or Neisseria well.