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 misuse a lack of knowledge on which antibiotic use generates the most risk to humans, policies and regulations have been placed to limit any harmful effects, such as the potential of bacteria developing antibiotic resistance within livestock, and that bacteria transferring resistance genes to human pathogens On January 1, 2017, the FDA enacted legislation to require that all human medically important feed-grade antibiotics (many prior over-the-counter-drugs) become classified as Veterinary Feed Directive drugs (VFD). This action requires that farmers establish and work with veterinaries to receive a written VFD order. The effect of this act places a requirement on an established