Table 1: Summary of first-line antimicrobial options for UTIs in the dog and cat.

Infection Type First-line drug options Uncomplicated UTI Amoxicillin, trimethoprim-sulfonamide Complicated Guided by culture and susceptibility testing, but consider amoxicillin or trimethoprim-sulfonamide initially Subclinical bacteriuria Antimicrobial therapy not recommended unless high risk for ascending infection. If so, treat as per complicated UTI Pyelonephritis Start with a fluoroquinolone, with re-assessment based on culture and susceptibility testing