Varieties of Staphylococcus aureus that are resistant to the drug methicillin . View Available Hint(s) Varieties of Staphylococcus aureus that are resistant to the drug methicillin . were strongly selected for as methicillin became widely used to treat bacterial infections do not have an advantage in the absence of methicillin All answers are correct. developed in response to the use of methicillin already existed in the population before methicillin was developed