Penicilli n year of Dis cov ery: 1928 What Is It?

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Pen i cil lin
PENICILLI N
PENICILLI N
Year of Dis cov ery: 1928
What Is It? The first com mer cially avail able an ti bi otic drug.
Who Dis cov ered It? Al ex an der Flem ing
Why Is This One of the 100 Great est?
Why Is This One of the 100 Great est?
Pen i cil lin has saved mil lions of lives—tens of thou sands dur ing the last years of World 
War II alone. The first an ti bi otic to suc cess fully fight bac te rial in fec tions and dis ease, pen i -
cil lin was called a mir a cle cure for a dozen killer dis eases ram pant in the early twentieth
century.
Pen i cil lin cre ated a whole new ar se nal of drugs in doc tors’ toolkits to fight dis ease and
in fec tion. It opened the door to en tire new fam i lies and new gen er a tions of an ti bi otic drugs.
Pen i cil lin started the vast in dus try of an ti bi otic drugs and ush ered in a new era of medicine.
How Was It Dis cov ered?
How Was It Dis cov ered?
In 1928, 47-year-old Scot tish born Al ex an der Flem ing was named chief bio chem ist at
St. Mary’s Hos pi tal in Lon don and given a base ment lab o ra tory tucked in next to the boiler
room.
As the staff bac te ri ol o gist, he grew (or “cul tured”) bac te ria in small, round, glass
plates for hos pi tal study and ex per i ment. Us ing mi cro scopic amounts of a bac te rium (of ten
col lected from a sick pa tient), he grew enough of each to de ter mine why the pa tient was sick 
and how best to fight the in fec tion. Small dishes of deadly staph y lo cocci, strep to cocci, and
pneumococci bac te ria were lined and la beled across the one lab bench that stretched the
length of Fleming’s lab.
Molds were the one great haz ard to Flem ing’s lab op er a tion. Flem ing’s lab al ter nated
be tween be ing drafty and stuffy, de pend ing on the weather and how hard the boiler worked
next door. His only ven ti la tion was a pair of win dows that opened at ground level to the
parklike gar dens of the hos pi tal. Af ter noon breezes blew leaves, dust, and a great va ri ety of
air borne molds through those win dows. It seemed im pos si ble to keep molds from drift ing
into, and con tam i nat ing, most of the bacteria Fleming tried to grow.
On Sep tem ber 28, 1928, Flem ing’s heart sank as he re al ized that a prized dish of pure
(and deadly) staph y lo cocci bac te ria had been ru ined by a strange, green mold. The mold
must have floated into the dish some time early the pre vi ous eve ning and had been mul ti ply -
ing since then. Green ish mold fuzz now cov ered half the dish.
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Flem ing grunted and sighed. Then he froze. Where this strange green mold had grown, 
the staph y lo cocci bac te ria had sim ply dis ap peared. Even bac te ria more than an inch from
the mold had turned trans par ent and sickly.
What kind of mold could de stroy one of the most hearty, te na cious, and deadly bac te ria
on earth? No other sub stance then known to man could at tack staph y lo cocci so suc cess fully.
It took two weeks for Flem ing to iso late and cul ture enough of the tough green mold to
com plete an iden ti fi ca tion: Penicillium notatum. Within a month he had dis cov ered that the
mold se creted a sub stance that killed bac te ria. He be gan to call this sub stance “penicillin.”
Through cul ture dish ex per i ments he dis cov ered that pen i cil lin could eas ily de stroy all 
the com mon hu man-kill ing bac te ria—staph y lo cocci, strep to cocci, pneumococci, even the
tough est of all, the ba cilli of diph the ria. The only bac te rium pen i cil lin fought but did not de -
stroy was the weak, sen si tive bac te rium that caused influenza (flu).
Flem ing spent six months test ing pen i cil lin on rab bits to es tab lish that the drug was
safe for hu man use be fore, in late 1929, an nounc ing the dis cov ery of his mir a cle mold that
had drifted in the window.
How ever, pen i cil lin was dif fi cult and slow to grow. It worked won ders but was avail -
able in such small quan ti ties that it did lit tle prac ti cal good. In 1942 Dor o thy Hodg kin, a
Brit ish re searcher, de vel oped a new pro cess, called X-ray crystalography, to de ci pher the
struc ture of a pen i cil lin mol e cule. It took her 15 months and thou sands of X-ray im ages of
the mol e cules in a pen i cil lin crys tal to iden tify each of the 35 at oms in a pen i cil lin mol e cule. 
Dr. Hodg kin was awarded the 1964 Nobel Prize for her work.
Amer i can doc tors Howard Flo rey and Ernst Chain were able to use Hodg kin’s map to
syn thet i cally pro duce pen i cil lin mol e cules in mass pro duc tion be gin ning in 1943. For their
ef fort, Flo rey and Chain were awarded the 1945 No bel Price in Med i cine jointly with Al ex -
an der Flem ing, the discoverer of penicillin.