People were ecstatic when British bacteriologist, Alexander Fleming, discovered penicillin. Fleming saw the drawbacks of the drug, though. In 1945 he cautioned people that the misuse of penicillin could lead to mutant forms of bacteria to grow that would resist the drug. He was absolutely right.
An estimated 14 percent of the staphylococcus strains isolated from patients in a London hospital had developed resistance to penicillin by 1946, just three years after the miracle drug was introduced. Penicillin was the stepping stone to other microbe killers.
Within three decades several more drugs had been introduced to combat bacteria and infections including amoxicillin, tetracycline, and streptomycin. By the 1970s, there were over 100 antibiotics on pharmacy shelves.
The U.S. Government de-emphasized the need and research for bacterial research, because it was becoming an oversaturated environment. They began conducting research on other health issues including vaccines. Bacteriology became a thing of the past.