Antibiotic Production

Antibiotics are chemical substances made by microorganisms that kill or slow the growth of other, disease-causing microbes even at very low concentration; the word literally means 'against life'. Selman Waksman discovered streptomycin and coined the term 'antibiotic' in 1943. The most celebrated discovery came when Alexander Fleming, while working with Staphylococcus cultures, noticed that a green mould contaminating one of his unwashed culture plates had created a bacteria-free zone around itself; he traced this to a chemical the mould secreted and named it penicillin, produced by the fungi Penicillium notatum and P. chrysogenum (Fig. 9.1). Penicillin is bactericidal — it kills bacteria outright by blocking synthesis of their cell wall — and is sometimes called the 'queen of drugs'. Its full therapeutic value was realised only when Ernest Chain and Howard Florey used it to treat wounded soldiers in the Second World War; Fleming, Chain and Florey shared the 1945 Nobel Prize for the discovery. Because penicillin can trigger a hypersensitivity reaction (nausea, vomiting, wheezing, even cardiovascular collapse), doctors first test a patient's sensitivity with a small forearm dose before full administration. Other antibiotics include the broad-spectrum, bacteriostatic tetracyclines (starting with chlortetracycline from Streptomyces aureofaciens) and the broad-spectrum, bactericidal streptomycin from Streptomyces griseus, especially effective against Mycobacterium tuberculosis, along with erythromycin, chloromycetin, griseofulvin, neomycin, kanamycin and bacitracin. Antibiotics are classed as broad-spectrum (active against many kinds of bacteria) or narrow-spectrum (active against a select group). Misuse and overuse of antibiotics, along with poor infection con …