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STREPTOMYCIN
An antibiotic produced by the mould Streplomyces griseus. Streptomycin is effective against several of the bacterial species which cause disease in man. It was first isolated by Selman A. Waksman, in the United States in 1944.
Streptomycin seemed at first to be an immensely valuable antibiotic for use against a wide range of infections, but it soon became apparent that the drug often produced serious damage to the hearing and balance mechanisms of the inner ear, particularly in elderly patients. Its use is now practically confined to the treatment of tuber- culosis, in which condition it is given in carefully controlled doses in combination with two other anti-tuberculous drugs, PAS (para-aminosalicylic acid) and INAH (isoniazid). The development of anti-tuberculous chemotherapy with these three drugs has been one of the greatest advances in medical history.
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SULPHONAMIDE
A compound containing the sulphonamide group (SO²NH²) or one of its derivatives. Many of the members of this group of compounds have antibacterial properties and they have been much used in the treatment of bacterial infections such as pneumonia, meningitis, septicaemia, and peritonitis. The advent of antibiotics in the 1940s greatly reduced the demand for sulphonamides so that they are now used principally in the treatment of meningitis and of urinary and intestinal infection, and (in the form of drops) for treating eye infections.
However, in the mid-1970s sulphonamides were given something of a. new lease of life. It was discovered that an extremely efficient antibacterial drug could be produced by combining sulpha- methoxazole with an antifolate agent called trimethoprim. The resulting combination, called cotrimoxazole, kills bacteria by interfering with their folate and purine synthesis. Cotrimoxazole rapidly became one of the most widely used drugs in medical practice, being prescribed in the treatment of urinary tract infections, and also in the treatment of streptococcal and staphylococcal respiratory tract infections.
Ordinary sulphonamides, however, are merely bacteriostatic (i.e. they stop the growth of bacteria) rather than bacteriocidal. Their bacteriostatic properties were discovered in 1932 (though not published until 1935) by the German scientist Gerhard Domagk. He observed that the sulphonamide compound known as Prontosil would pro- tect mice from lethal infection with streptococci (Domagk was awarded the Nobel Prize for medicine in 1939, but the Nazis would not let him accept it.) This observation rapidly led to the discovery that it was not Prontosil itself that protected the mice, but the substance sulphanilamide which was only part of the Prontosil molecule. The mechanism of this antibacterial activity was worked out by two British scientists, D. D. Woods and P. Fildes, who realized that sulphanilamide had a chemical structure very similar to that of a normal bacterial metabolite known as para-aminobenzoic acid. These scientists were able to show that in bacteria exposed to sulphanilamide the enzyme which normally metabolized para-aminobenzoic acid became blocked with the structurally similar sulphanilamide. As a consequence bacterial metabolism stopped, the bacteria ceased to grow, and the infection was readily eliminated by the body's natural defences
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