Application of the Formula for Rational Antimicrobial Therapy (FRAT) to Community-Acquired Pneumonia

Community-acquired pneumonia (CAP) remains a common condition for which patients seek medical advice in the outpatient setting and where antimicrobial agents are prescribed empirically–often based on therapeutic guideline recommendations. Antimicrobial resistance impacts on therapeutic choices as resistance is associated with clinical failure which in turn may impact morbidity and mortality. The Formal for Rational Antimicrobial Therapy (FRAT) considers etiology and antimicrobial susceptibility to generate a factor to predict the likely activity of an antimicrobial agent in CAP or any other infection for which etiology and susceptibility data can be considered. In considering the FRAT formula in CAP, amoxicillin and macrolides offer a predictability of 52.6-78.3% whereas for trimethoprim/sulfamethoxazole the predictability was 45.2% as compared to 90.1% for tetracyclines/doxycycline and 98.2% for levofloxacin (and moxifloxacin). The FRAT formula clearly differentiates antimicrobial agents based on spectrum of activity and impact of antimicrobial resistance and provides yet another factor for consideration in the selection of an antimicrobial agent for treatment of CAP.