Penicillin: The most famous of all antibiotics, named for the fungal mold Penicillium notatum from which it is derived. Penicillin acts by destroying the cell wall of bacteria.

Penicillin is active against a number of types of bacteria including Streptococcus pneumoniae, Listeria, Neisseria gonorrhoea, Clostridium, Peptococcus, and Peptostreptococcus.

Most staphylococci now are resistant to penicillin. Today, manyderivatives of penicillin are available which act on more types of bacteria than penicillin itself.

The name "penicillium" was taken from the Latin "penicillum" meaning "a painter's brush" because the fronds of the fungus were thought to look like a painter's brush.

For information about the pharmacology of penicillin, see Penicillin V, See also: Penicillin history.