Context: The emergence of resistance of bacteria to antibiotics is a common phenomenon. Emergence of resistance often reflects evolutionary processes that take place during 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.

Question: What does emergence of resistance reflect?
Answer: evolutionary processes

Question: What is the purpose of antibiotic treatment?
Answer: survive high doses of antibiotics

Question: When was antibacterial-resistance demonstrated?
Answer: 1943

Question: Who made the demonstration in 1943?
Answer: Luria–Delbrück

Question: What is a modern common occurence with antibiotics?
Answer: resistance of bacteria

Question: What is resistance to antibiotics a cause of?
Answer: evolution

Question: When was the Luria-Delbruck experiment?
Answer: 1943

Question: Which two antibiotics that have high efficacy are much less useful now?
Answer: penicillin and erythromycin

Question: What does emergence of bacteria reflect?
Answer: Unanswerable

Question: What is the purpose of bacterial strains?
Answer: Unanswerable

Question: When were bacterial species and strains invented?
Answer: Unanswerable

Question: What is a modern occurrence with high doeses?
Answer: Unanswerable

Question: What is resistance to genes a cause of?
Answer: Unanswerable