Bacterial infections once killed routinely; antibiotics changed that. An antibiotic is a substance that kills bacteria or stops their growth, allowing the host immune system to clear the infection.

Different classes target cell walls, protein synthesis, DNA replication, or other bacterial processes. Choice depends on the likely organism, local resistance patterns, site of infection, and patient factors such as allergy and kidney function. Antibiotics have no effect on viruses, so using them for colds or influenza is both useless and harmful.

Resistance develops when bacteria adapt under selective pressure. Stewardship programs promote correct drug, dose, and duration to preserve effectiveness. Completing prescribed courses and avoiding leftover antibiotics remain practical patient responsibilities that support the same goal.

• Agent that kills or inhibits bacteria
• Selected according to organism and patient factors
• Ineffective against viruses
• Must be used judiciously to limit resistance