Add to ORKGIndividual reprints of this article and a bound reprint of the entire Symposium on Antimicrobial Therapy will be available for purchase from our Web site www.mayoclinicproceedings.com. © 2011 Mayo Foundation for Medical Education and Research For editorial comment, see page 86 The terms antimicrobial, antibiotic, and anti-infective encompass a wide variety of pharmaceutical agents that include antibacterial, antifungal, antiviral, and anti-parasitic drugs. Of these, antibacterial agents are by far the most commonly used and thus are the focus of this article, although similar principles apply to the other agents as well. Evidence-based practice guidelines from the Infec-tious Diseases Society of America1 can help direct appro-priate therapy...