Diagnostic testing, including culture and susceptibility testing, aids in the appropriate selection of antimicrobials.

• When a urinary tract infection (UTI) (also known as bacterial cystitis) is suspected, urine collected by cystocentesis can help distinguish true bacteriuria from contamination but is not able to distinguish infection from subclinical bacteriuria.
• Poor urine concentrating ability is a risk factor for bacteriuria. Urine culture coupled with the presence of lower urinary tract signs may be the only way to identify infection in such cases.¹⁵
• The presence of bacteriuria, in the absence of lower urinary tract signs, does not necessarily indicate a UTI and is considered subclinical bacteriuria, which generally does not require antimicrobial treatment.¹⁵
• Antimicrobial susceptibility testing to provide an interpretation of susceptible, intermediate, or resistant to antimicrobial drugs should be done to guide the selection of antimicrobials. Veterinarians should ensure that their reference laboratories use species-specific (i.e., cats and dogs) susceptibility testing breakpoints where available.
• Performing cytological evaluation of patient samples or body sites is important in advance of and as a complement to culture and antimicrobial susceptibility testing.
• Because certain antimicrobials are more effective against gram-positive or gram-negative organisms, interim antimicrobial decisions can be based on gram stain and the site of infection.