I want to know the answer to the following question:
Which two antibiotics that have high efficacy are much less useful now?
All the background I'm provided with is that "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.". Is that enough to answer the question?
Answer: yes