When Should Antimicrobial Susceptibility Testing Be Performed on a Bacterial

When should antimicrobial susceptibility testing be performed on a bacterial isolate from a clinical specimen?

A) When the isolate is determined to be a probable cause of the patient's infection
B) When the susceptibility of the isolate to particular antimicrobial agents cannot be reliably predicted
C) When the organism is part of the normal microbiota
D) Both A and B