antibiotic

Before antibiotics, a simple cut or a routine infection could kill, because the body sometimes lost the race against invading bacteria. An antibiotic is a medicine that helps win that race — a chemical that kills bacteria or stops them from multiplying, giving your immune system time to mop up. The discovery of penicillin from a mold in 1928 opened an age in which once-deadly bacterial diseases became, for a while, easily curable.

Antibiotics work by attacking structures or processes that bacterial cells have but your cells do not — a principle called selective toxicity. Some, like penicillin, block construction of the peptidoglycan cell wall, so the growing bacterium bursts. Others jam the bacterial ribosome (which differs from your ribosomes) to stop protein-making, or block bacterial enzymes that copy DNA. Because they aim at bacteria-specific targets, a good antibiotic can poison the invader while leaving your own cells largely unharmed.

The single most important honest point about antibiotics is what they cannot do: they have no effect on viruses, because viruses are not cells and lack the bacterial targets antibiotics aim at. Taking an antibiotic for a cold or the flu does nothing for the illness and actively contributes to antibiotic resistance by killing off the harmless bacteria and selecting for the tough ones. Antibiotics are also not painkillers or general 'feel-better' pills — they are precision weapons against bacteria, and using them carelessly slowly blunts the whole arsenal.