Antimicrobial AgentsAntimicrobial agents are some of the most frequently used medications throughout the world. When prescribing these drugs, providers must take into consideration information such asdiagnosing the correct infection, knowing the difference between empiric and definitive therapy, knowing when to change to narrow-spectrum agents, understanding the pharmacodynamics and effectiveness of the medication, and recognizing the adverse effects the medication may have (Leekha, Terrell, & Edson, 2011). The purpose of this paper is to identify and describe the categories of antimicrobial agents, identify the differences between viral and bacterial infections,and provide an explanation of why proper identification of infections is key in the selection of the appropriate antimicrobial agent.Categories of Antimicrobial AgentsAntimicrobial agents should be carefully selected depending on the site and type of infection the patient presents with. Frequently, empiric treatment is started be selecting an antimicrobial that could be most effective on the possible pathogen. The antimicrobial should not be started until microbiological cultures are obtained. There are many different categories of antimicrobials that have different clinical uses, mechanism of action, and spectrum of activity.Penicillin: Used since 1928. They inhibit bacterial growth by interfering with cell wall synthesis. It is used frequently in the treatment infections of the urinary tract, upper and lower respiratory tract, and central nervous system (CNS).Beta-Lactam/Beta-Lactamase Inhibitor: They stop the degradation of beta-lactam by the organism that incapacitates penicillin. Used in the treatment of polymicrobial infections, skin and soft tissue infections, and respiratory tract infections.