6.13—Bacteriostatic and bactericidal antibiotics

Bactericidal antibiotics kill bacterial cells, whereas bacteriostatic antibiotics inhibit growth so the immune system can remove the slowed population. At a sufficiently high dose, a bacteriostatic drug may become lethal.

Antibiotics target bacterial structures or processes such as murein-wall synthesis, ribosomes, membranes or DNA handling. Human cells and viruses lack the corresponding bacterial targets.

A drug that prevents a strong bacterial wall can cause osmotic lysis; one that binds bacterial ribosomes can halt protein synthesis without directly bursting the cell.

Antibiotics do not treat viruses, and “no growth” is not the same as “no viable cells”. The drug mechanism and target determine the outcome.