Antibiotics are defined as chemical substances produced by living organisms, generally a microorganism, that is harmful to other microorganisms. These compounds are formed naturally by fungi and bacteria, and are then released into the soil as part of nature's production chain. Penicillin was first discovered by Dr. Alexander Fleming back in 1928; however it was not until the early 1940's, that Penicillin began to be mass produced. The drug played a large role in treating the soldiers of WWII.
Since then, numerous other antibiotics have been discovered, synthesized in the laboratory and come into general use. It is important to remember that Antibiotics do not have any effect against viruses, which cause a large proportion of Upper Respiratory Tract infections in the US and western countries. In addition, many bacteria can develop mutations over a period of months or years; these mutations often make the bacteria resistant to the effects of Antibiotics. Acquired Antibiotic resistance is becoming a significant healthcare problem in the US and elsewhere. For example, a bacterium (Enteroccci) that has previously been sensitive only to the antibiotic Vancomycin has recently been shown to be developing resistant strains!
While development of newer antibiotics is underway, this takes time and is not easy. For now, the judicious use of these important medications remains the best way to limit the development of antibiotic resistant bacteria. In other words, physicians and patients should use these only when it is likely that they will be of value. Antibiotics have no role in the treatment of colds, the flu, etc., unless these infections are complicated by bacterial infection.