Beverly Lopez, age 12, of Nashville, Tenn., for her question:

WHEN WAS PENICILLIN DISCOVERED?

Penicillin is an antibiotic derived from the mold called Penicillium notatum. The action of this antibiotic was first observed in 1928 by the British bacteriologist Alexander Flaming, but it was another 10 years before penicillin was concentrated and studied by the British biochemist Ernst Chain, the British pathologist Sir Howard Florey and other scientists.

Penicillan acts both by killing bacteria and by inhibiting their growth. It does not kill organisms in the resting stage but only those that are growing and reproducing.

Penicillin is effective against a wide range of disease bearing microorganisms. The drug has been successfully employed to treat many diseases.

The strength and dosage of penicillin are measured in terms of internal units.

In early days of penicillin therapy, the drug was administered every three or four hours in small doses. More recently a preparation called benzathine penicillin G has been produced that provides detectable levels of antibiotic for as long as four weeks after a single intramuscular injection.

Penicillin is an antibiotic derived from the mold called Penicillium notatum. The action of this antibiotic was first observed in 1928 by the British bacteriologist Alexander Flaming, but it was another 10 years before penicillin was concentrated and studied by the British biochemist Ernst Chain, the British pathologist Sir Howard Florey and other scientists.

Penicillan acts both by killing bacteria and by inhibiting their growth. It does not kill organisms in the resting stage but only those that are growing and reproducing.

Penicillin is effective against a wide range of disease bearing microorganisms. The drug has been successfully employed to treat many diseases.

The strength and dosage of penicillin are measured in terms of internal units.

In early days of penicillin therapy, the drug was administered every three or four hours in small doses. More recently a preparation called benzathine penicillin G has been produced that provides detectable levels of antibiotic for as long as four weeks after a single intramuscular injection.