Antibiotics

The chapter's antibiotic case studies form a connected historical narrative. Arsenic compounds had long been known to be highly poisonous to humans; the German bacteriologist Paul Ehrlich deliberately investigated arsenic-based organic compounds in a search for a substance toxic enough to kill the syphilis-causing organism but safe enough for a patient to tolerate, and this work led him to discover the first effective treatment for syphilis, a synthetic antibiotic he named salvarsan -- work for which he was awarded the 1908 Nobel Prize in Medicine. Ehrlich went on to notice a structural resemblance between salvarsan and the azo dyes, and pursuing that resemblance further, he succeeded in synthesising an effective diazo antibacterial compound, prontosil, in 1932. It was subsequently discovered that, once inside the body, prontosil is converted into a chemically simpler compound, sulphanilamide (a benzene ring bearing a -NH2 group and, para to it, a -SO2NH2 sulphonamide group) -- and this discovery opened up an entire new direction in drug design, leading to a wide range of related 'sulpha drugs' built on the same sulphanilamide-type sulphonamide core, of which sulphapyridine (sulphanilamide linked to a pyridine ring) was one of the most effective. In 1929, Alexander Fleming discovered that a Penicillium mould possessed antibacterial properties; establishing the clinical usefulness of its purified active ingredient, penicillin, as an antibiotic drug took a further thirteen years of work, but penicillin stands as the first antibiotic of microbial origin. Chloramphenicol, isolated in 1947, is a second antibiotic of microbial origin discussed in the chapter. Bringing these examples together, the chapter classifies antibiotics into three types by how wide a range of bacteria they act against: broad-spectrum antibiotics are effective against a wide range of bacterial species; narrow-spectrum antibiotics are effective against only one particular group of bacteria; and limited-spectrum antibiotics are effective against a single organism specifically. A stated disadvantage …