Final answer:
Alexander Fleming's research using mold in 1928 was the first event to occur, which led to the discovery of penicillin, predating its confirmation as a microbe killer, its mass production during World War II, and its general use to treat diseases.
Step-by-step explanation:
The first event to occur regarding penicillin was when Alexander Fleming did research using mold which led to the discovery of penicillin. In 1928, Fleming observed antibacterial properties in mold growing on a bacterial culture plate, which subsequently was identified as Penicillium notatum. This discovery was monumental as it led to the first antibiotic, and further tests confirmed that penicillin kills microbes such as staphylococci, streptococci, meningococci, and Corynebacterium diphtheriae. After the discovery, the drug's mass production and efficacy tests were conducted by Howard Florey and Ernst Chain, which allowed penicillin to be used widely in World War II to save many lives. Lastly, penicillin began to be used to treat many diseases. Therefore, the correct order of events is: Fleming's research on mold, confirmation of penicillin's microbe-killing properties, mass production and use in World War II, and the general treatment of diseases.