Which of the following is a bactericidal antibiotic?

First, let us recall the basic definition: an antibiotic that kills bacteria outright is called a bactericidal antibiotic, whereas one that merely inhibits their growth is termed bacteriostatic. With this key distinction in mind, we shall now examine each option in turn.

We have fluoroquinolones such as ofloxacin. Their mechanism involves the inhibition of bacterial DNA gyrase and topoisomerase IV. Because this action directly disrupts DNA replication, the bacterial cell cannot survive, and cell death follows. Hence, ofloxacin is classified as a bactericidal antibiotic.

Now consider tetracycline. This drug binds reversibly to the $$30\,\text{s}$$ ribosomal subunit and prevents the attachment of aminoacyl tRNA. The ribosome stalls, protein synthesis stops, yet the bacterial cell is not instantly destroyed; growth is merely halted. Therefore tetracycline is bacteriostatic, not bactericidal.

Next comes chloramphenicol. It binds to the $$50\,\text{s}$$ subunit and blocks peptidyl transferase activity. Because the binding is again mainly reversible, the drug is usually placed in the bacteriostatic group.

Finally, erythromycin belongs to the macrolide family. It attaches to the $$50\,\text{s}$$ ribosomal subunit as well, specifically inhibiting translocation. The effect is growth inhibition without immediate killing, so erythromycin is also bacteriostatic.

Putting all this information together, only ofloxacin among the given choices actually kills bacteria directly; the remaining three merely inhibit growth.

Hence, the correct answer is Option A.