Impact:

In 1943, Johnson cultured cells from the wound of a 7-year-old girl, Margaret Tracy, who had been taken to Presbyterian Hospital’s emergency room for treatment of a leg injury. Initial microscopic examination of the wound revealed that it was infected with the bacterium Staphylococcus aureas. Subsequent microscopic examination revealed that the Staph cells had disappeared overnight. Johnson discovered that another microbe in the sample, bacillus subtilis, had killed the Staph cells. She purified and concentrated the bacillus strain, leading to the development of a new antibiotic called Bacitracin (a combination of Bacillus and Tracy). The FDA approved Bacitracin in 1948. The topical ointment is widely used today, alone or in combination with other antibiotics.