Resistance to anti-infective drugs is a global health challenge that is progressing year after year. The followings are examples of nonacquired resistance except: a. Resistance of gram negative bacteria to vancomycin b. Resistance of anaerobic bacteria to aminoglycosides c. Resistance of mycoplasma to B-lactams d. Resistance of cytomegalovirus to acyclovir e. Resistance of staphylococcus aureus to methicillin