Penicillin is a group of antibiotics originally derived from Penicillium molds, notably P. chrysogenum and P. rubens
. It was the first widely used antibiotic, discovered in 1928 by Alexander Fleming, who observed that the mold produced a substance that killed bacteria
. Penicillin works by breaking down the cell walls of bacteria, weakening them and allowing the body's immune system to fight the infection
. Penicillins are effective against many bacterial infections such as strep throat, ear infections, urinary tract infections, pneumonia, and syphilis
. There are several types of penicillin, including penicillin G (administered by injection) and penicillin V (taken orally), as well as related antibiotics like amoxicillin and ampicillin
. Penicillin is generally safe but can cause side effects, including allergic reactions ranging from mild rashes to severe anaphylaxis, which is rare but serious
. Despite widespread use, some bacteria have developed resistance to penicillin
. In summary, penicillin is a foundational antibiotic medication used to treat a broad range of bacterial infections by targeting bacterial cell walls, originally derived from mold and discovered nearly a century ago
