Inhibition in a culture dish
In 1928, Alexander Fleming at St Mary’s Hospital in London noticed that staphylococcal growth was inhibited near a Penicillium mould. He cultivated the mould and investigated the effects of its culture fluid on different bacteria. His paper appeared in the British Journal of Experimental Pathology in 1929, preserving methods, comparisons and results from the investigation.
References: [1]
Comparing bacterial responses
Fleming named the active material in the culture fluid penicillin. Dilution and culture experiments compared bacterial sensitivity: some pathogens were strongly inhibited, while others continued growing. He also examined how culture conditions affected activity. Inhibition became more than a striking appearance in one dish; it could be investigated repeatedly and compared under different experimental conditions.
References: [1]
Laboratory use and the problem of extraction
The paper explored using penicillin to suppress unwanted bacteria while isolating the influenza bacillus, and considered possible therapeutic use. Treatment would require enough active material, stability and knowledge of its effects in the body. The substance was difficult to extract from culture fluid. The early work chiefly supplied antibacterial evidence and experimental procedures that later chemical and pharmacological investigations could pursue.
A team developed the therapeutic investigation
Howard Florey, Ernst Chain, Norman Heatley and colleagues at Oxford later investigated penicillin again. They improved extraction and assays, tested its effects in experimentally infected animals, and published their findings in The Lancet in 1940. Culture work, chemical preparation and infection experiments combined to support subsequent clinical and production work. Fleming’s paper and these later studies formed successive stages in penicillin’s development for medicine.