Broad-spectrum antibiotic their greater potential to disrupt a larger variety of normal human flora. After continued exposure to an antibiotic, bacteria may develop changes in their structure or function that make them resistant to the antibiotic. These resistant organisms will live, while the susceptible organisms will die, leaving the population of bacteria entirely resistant to a given antibiotics. For example, after the discovery of penicillin and its subsequent use to treat bacterial infections, bacteria were found to have begun producing an enzyme, penicillinase, which rendered the penicillin molecule inactive. In response to this newly-acquired resistance, newer penicillins were produced that could not
Antibiotic prophylaxis 2006 against antibiotics for growth promotion purposes. It was estimated in 2014 that over 80% of the world's antibiotic use was on farms. Coccidiosis in fowl had evolved increased tolerance to the antibiotic feed. The WHO warned in April 2014 that farm use was a contributor to superbugs in humans. The Auditor General of Canada found lack of progress in 2014 on antimicrobial resistance despite three years of government funds that should have been used to implement a reduction programme. A CBC writer was concerned that there was in Canada "no coordinated national system to control antibiotics in agriculture." Due