Question

varieties of staphylococcus aureus that are resistant to the drug methicillin _______. do not have an advantage in the absence of methicillin already existed in the population before methicillin was developed were strongly selected for as methicillin became widely used to treat bacterial infections all answers are correct.

Explanation:

1. In the absence of methicillin, methicillin - resistant Staphylococcus aureus (MRSA) may not have a growth or survival advantage over non - resistant strains as the selective pressure of the drug is not present.
2. Mutations conferring methicillin resistance likely already existed in the Staphylococcus aureus population as spontaneous genetic variations occur naturally before the drug was developed.
3. As methicillin was widely used, it created a strong selective pressure, favoring the survival and proliferation of MRSA strains.

Answer:

D. All answers are correct.