`=>` Antibiotics are used as drugs to treat infections because of their low toxicity for humans and animals.
`=>` Initially antibiotics were classified as chemical substances produced by microorganisms (bacteria, fungi and molds) that inhibit the growth or even destroy microorganisms.
`=>` The development of synthetic methods has helped in synthesising some of the compounds that were originally discovered as products of microorganisms.
`=>` Also, some purely synthetic compounds have antibacterial activity, and therefore, definition of antibiotic has been modified.
`color{green}("Antibiotic ")` : An antibiotic now refers to a substance produced wholly or partly by chemical synthesis, which in low concentrations inhibits the growth or destroys microorganisms by intervening in their metabolic processes.
`=>` The search for chemicals that would adversely affect invading bacteria but not the host began in the nineteenth century.
`=>` Paul Ehrlich, a German bacteriologist, conceived this idea. He investigated arsenic based structures in order to produce less toxic substances for the treatment of syphilis.
● He developed the medicine, `text(arsphenamine)`, known as `color{green}("salvarsan")`.
● Paul Ehrlich got Nobel prize for Medicine in 1908 for this discovery.
● It was the first effective treatment discovered for syphilis.
● Although salvarsan is toxic to human beings, its effect on the bacteria, spirochete, which causes syphilis is much greater than on human beings.
● At the same time, Ehrlich was working on azodyes also. He noted that there is similarity in structures of salvarsan and azodyes.
● The `color{red}(–As = As–)` linkage present in arsphenamine resembles the `color{red}(–N = N –)` linkage present in azodyes in the sense that arsenic atom is present in place of nitrogen.
● He also noted tissues getting coloured by dyes selectively.
● Therefore, Ehrlich began to search for the compounds which resemble in structure to azodyes and selectively bind to bacteria.
● In 1932, he succeeded in preparing the first effective antibacterial agent, prontosil, which resembles in structure to the compound, salvarsan.
● Soon it was discovered that in the body prontosil is converted to a compound called sulphanilamide, which is the real active compound.
● Thus the sulpha drugs were discovered. A large range of sulphonamide analogues was synthesised. One of the most effective is sulphapyridine.
`=>` Despite the success of sulfonamides, the real revolution in antibacterial therapy began with the discovery of Alexander Fleming in 1929, of the antibacterial properties of a Penicillium fungus.
`=>` Isolation and purification of active compound to accumulate sufficient material for clinical trials took thirteen years.
`=>` Antibiotics have either cidal (killing) effect or a static (inhibitory) effect on microbes.
`=>` A few examples of the two types of antibiotics are as follows:
`color{red}(tt ( ( text{Bactericidal} , text{Bacteriostatic}) , ( text{Penicillin} , text{Erythromycin}) , ( text{Aminoglycosides} , text{Tetracycline}) , (text{Ofloxacin} , text{Chloramphenicol})))`
`=>` The range of bacteria or other microorganisms that are affected by a certain antibiotic is expressed as its spectrum of action.
`color{green}("Broad Spectrum Antibiotics ")` : Antibiotics which kill or inhibit a wide range of Gram-positive and Gram-negative bacteria are said to be broad spectrum antibiotics.
`color{green}("Narrow Spectrum Antibiotics ")` : Those effective mainly against Gram-positive or Gram-negative bacteria are narrow spectrum antibiotics.
`color{green}("Limited Spectrum Antibiotics ")` : If effective against a single organism or disease, they are referred to as limited spectrum antibiotics.
● Penicillin `color{red}(G )`has a narrow spectrum.
● Ampicillin and Amoxycillin are synthetic modifications of penicillins. These have broad spectrum.
● It is absolutely essential to test the patients for sensitivity (allergy) to penicillin before it is administered.
● In India, penicillin is manufactured at the Hindustan Antibiotics in Pimpri and in private sector industry.
`=>` Chloramphenicol, isolated in 1947, is a broad spectrum antibiotic.
● It is rapidly absorbed from the gastrointestinal tract and hence can be given orally in case of typhoid, dysentery, acute fever, certain form of urinary infections, meningitis and pneumonia.
● Vancomycin and ofloxacin are the other important broad spectrum antibiotics.
● The antibiotic dysidazirine is supposed to be toxic towards certain strains of cancer cells.
`=>` Antibiotics are used as drugs to treat infections because of their low toxicity for humans and animals.
`=>` Initially antibiotics were classified as chemical substances produced by microorganisms (bacteria, fungi and molds) that inhibit the growth or even destroy microorganisms.
`=>` The development of synthetic methods has helped in synthesising some of the compounds that were originally discovered as products of microorganisms.
`=>` Also, some purely synthetic compounds have antibacterial activity, and therefore, definition of antibiotic has been modified.
`color{green}("Antibiotic ")` : An antibiotic now refers to a substance produced wholly or partly by chemical synthesis, which in low concentrations inhibits the growth or destroys microorganisms by intervening in their metabolic processes.
`=>` The search for chemicals that would adversely affect invading bacteria but not the host began in the nineteenth century.
`=>` Paul Ehrlich, a German bacteriologist, conceived this idea. He investigated arsenic based structures in order to produce less toxic substances for the treatment of syphilis.
● He developed the medicine, `text(arsphenamine)`, known as `color{green}("salvarsan")`.
● Paul Ehrlich got Nobel prize for Medicine in 1908 for this discovery.
● It was the first effective treatment discovered for syphilis.
● Although salvarsan is toxic to human beings, its effect on the bacteria, spirochete, which causes syphilis is much greater than on human beings.
● At the same time, Ehrlich was working on azodyes also. He noted that there is similarity in structures of salvarsan and azodyes.
● The `color{red}(–As = As–)` linkage present in arsphenamine resembles the `color{red}(–N = N –)` linkage present in azodyes in the sense that arsenic atom is present in place of nitrogen.
● He also noted tissues getting coloured by dyes selectively.
● Therefore, Ehrlich began to search for the compounds which resemble in structure to azodyes and selectively bind to bacteria.
● In 1932, he succeeded in preparing the first effective antibacterial agent, prontosil, which resembles in structure to the compound, salvarsan.
● Soon it was discovered that in the body prontosil is converted to a compound called sulphanilamide, which is the real active compound.
● Thus the sulpha drugs were discovered. A large range of sulphonamide analogues was synthesised. One of the most effective is sulphapyridine.
`=>` Despite the success of sulfonamides, the real revolution in antibacterial therapy began with the discovery of Alexander Fleming in 1929, of the antibacterial properties of a Penicillium fungus.
`=>` Isolation and purification of active compound to accumulate sufficient material for clinical trials took thirteen years.
`=>` Antibiotics have either cidal (killing) effect or a static (inhibitory) effect on microbes.
`=>` A few examples of the two types of antibiotics are as follows:
`color{red}(tt ( ( text{Bactericidal} , text{Bacteriostatic}) , ( text{Penicillin} , text{Erythromycin}) , ( text{Aminoglycosides} , text{Tetracycline}) , (text{Ofloxacin} , text{Chloramphenicol})))`
`=>` The range of bacteria or other microorganisms that are affected by a certain antibiotic is expressed as its spectrum of action.
`color{green}("Broad Spectrum Antibiotics ")` : Antibiotics which kill or inhibit a wide range of Gram-positive and Gram-negative bacteria are said to be broad spectrum antibiotics.
`color{green}("Narrow Spectrum Antibiotics ")` : Those effective mainly against Gram-positive or Gram-negative bacteria are narrow spectrum antibiotics.
`color{green}("Limited Spectrum Antibiotics ")` : If effective against a single organism or disease, they are referred to as limited spectrum antibiotics.
● Penicillin `color{red}(G )`has a narrow spectrum.
● Ampicillin and Amoxycillin are synthetic modifications of penicillins. These have broad spectrum.
● It is absolutely essential to test the patients for sensitivity (allergy) to penicillin before it is administered.
● In India, penicillin is manufactured at the Hindustan Antibiotics in Pimpri and in private sector industry.
`=>` Chloramphenicol, isolated in 1947, is a broad spectrum antibiotic.
● It is rapidly absorbed from the gastrointestinal tract and hence can be given orally in case of typhoid, dysentery, acute fever, certain form of urinary infections, meningitis and pneumonia.
● Vancomycin and ofloxacin are the other important broad spectrum antibiotics.
● The antibiotic dysidazirine is supposed to be toxic towards certain strains of cancer cells.