Table 2.

Proposed definitions of terminology to describe a day of therapy with a particular antimicrobial agent

Term	Definition	Examples
Unnecessary	Use of antimicrobials for non-infectious syndromes, use of antibiotics for non-bacterial infections, days of therapy beyond the indicated duration of therapy absent any clinical reason for a lengthened course, use of redundant antimicrobial therapy, and/or continuation of empiric broad-spectrum therapy when cultures have revealed the infecting pathogen.	Treatment of asymptomatic bacteriuria outside of established indications. Antibiotics for viral upper respiratory tract infections. Treating community-acquired pneumonia for 14 days instead of 5–7 in the absence of clinical data suggesting need for a longer course. Double anaerobic coverage. Continued use of vancomycin started empirically after growth of Pseudomonas aeruginosa in blood cultures. Continued use of empiric vancomycin and cefepime in a patient found to have sterile pancreatic necrosis.
Inappropriate	Use of antimicrobials in the setting of established infection to which the pathogen is resistant or use of antimicrobials not recommended in treatment guidelines.	Patient treated with an antibiotic not treating the bacteria recovered in cultures (bug-drug mismatch). Use of piperacillin/tazobactam to treat uncomplicated community acquired pneumonia.
Sub-optimal	Use of antimicrobials in the setting of established infection that can be improved in one of the following categories: 1) drug choice, 2) drug route, and 3) drug dose	Use of an overly broad-spectrum agent to treat a susceptible bacterium (e.g., cefepime for ampicillin susceptible E. coli infection). Use of intravenous fluoroquinolones when no contraindication to oral therapy. Failure to adjust doses of renally cleared drugs in the setting of acute renal failure.