Antibiotic antibiotic therapy. The antibiotic treatment may select for bacterial strains with physiologically or genetically enhanced capacity to survive high doses of antibiotics. Under certain conditions, it may result in preferential growth of resistant bacteria, while growth of susceptible bacteria is inhibited by the drug. For example, antibacterial selection for strains having previously acquired antibacterial-resistance genes was demonstrated in 1943 by the Luria–Delbrück experiment. Antibiotics such as penicillin and erythromycin, which used to have a high efficacy against many bacterial species and strains, have become less effective, due to the increased resistance of many bacterial strains. Resistance may take the form
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