What types of experiments were required to determine if the penicillium extract was safe and killed bacteria?

Alexander Fleming discovered the penicillin in 1928. He noticed that some bacteria he had left in a petri dish had been killed by naturally occurring penicillium mould. The penicillin began the era of antibiotics, has been recognized as one of the greatest advances in therapeutic medicine. The research required to determine if the penicillium extract was safe and killed bacteria was done at Oxford University. P rogram of animal experiments and clinical trials was carried.