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 use in livestock cover all these areas and instead focuses on the use of antibiotics for growth promotion, which has been banned in Europe since 2006, and on legislation regarding antibiotic use in farm animals in the USA. In 2013, the CDC finalized and released a report detailing antibiotic resistance and classified the top 18 resistant bacterium as either being urgent, serious or concerning threats. Of those organisms, three ("C. diff", carbapanem-resistant enterobacteriaceae, and "Neisseria gonorrhoeae") have been classified as urgent threats and require more monitoring and prevention. In the US alone, more than 2 million people are diagnosed with antibiotic-resistant infections and