Final answer:
The statement is true; Alexander Fleming discovered the first antibiotic, penicillin, in 1928 when he noticed that a mold inhibited the growth of Staphylococcus aureus. Penicillin was extensively studied and mass-produced by the early 1940s, revolutionizing the treatment of bacterial infections.
Step-by-step explanation:
The statement that in 1928, Alexander Fleming observed that the growth of the bacterium Staphylococcus aureus was inhibited by a mold, thereby discovering the first antibiotic, is true. This accidental finding in his laboratory at St. Mary's Hospital in London led to the discovery of penicillin, the world's first natural antibiotic.
Penicillin was initially found to be antibacterial against Staphylococcus aureus, streptococci, meningococci, and Corynebacterium diphtheriae, the agent of diphtheria. Subsequent work by other scientists such as Howard Florey and Ernst Chain led to the development of methods to mass produce penicillin for clinical use, and it was made widely available by 1944 for treating bacterial infections.