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 synergy conventional antibiotics. Antibiotic synergy Antibiotic synergy is one of three responses possible when two or more antibiotics are used simultaneously to treat an infection. In the synergistic response, the applied antibiotics work together to produce an effect more potent than if each antibiotic were applied singly. Compare to the additive effect, where the potency of an antibiotic combination is roughly equal to the combined potencies of each antibiotic singly, and antagonistic effect, where the potency of the combination is less than the combined potencies of each antibiotic. Clinical interest in synergism dates back to the early 1950s when practitioners noted