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 use in livestock of antibiotic usage in livestock transferring to humans has been well documented for over 40 years. It was first documented in 1976, where a study followed a novel antibiotic being used in livestock. The bacteria in animals and workers were regularly followed to record translational effects. The findings revealed that within 2 weeks, the bacteria found in the guts of animals fed antibiotics were resistant to the new antibiotic. Additionally, the resistant bacteria had spread to farm's laborers within 6 months. The bacteria in the stool of the laborers were tested and contained more than 80% resistance to the initial