Assessing the urinary concentration of nitrofurantoin and its antibacterial activity against Escherichia coli, Staphylococcus pseudintermedius, and Enterococcus faecium isolated from dogs with urinary tract infections

Prevalence and antimicrobial resistance of bacteria isolated from urine samples of cats with urinary tract infections in Illinois, United States of America

Information on antimicrobial resistance patterns of urinary pathogens of cats can aid veterinarians in their antimicrobial prescription choices. We assessed the prevalence and antimicrobial resistance of bacteria isolated from urine samples of cats with urinary tract infections (UTIs) submitted to a veterinary diagnostic laboratory in Illinois between 2020 and 2022. The laboratory received 2026 urine samples during the study period, of which 606 (29.97%) showed bacterial growth, and from these samples, 883 bacterial strains were recovered. The most common gram-positive bacterial species included Enterococcus faecalis (n = 123), Staphylococcus felis (n = 50), and Staphylococcus pseudintermedius (n = 28), while the most common gram-negative bacteria included Escherichia coli (n = 322) and Proteus mirabilis (n = 18). Among the gram-positive isolates, none of the Enterococcus faecalis isolates showed resistance to amoxicillin-clavulanic acid and ampicillin. In addition, Staphylococcus felis isolates showed low resistance to ampicillin (7.32%), enrofloxacin (4.88%), and amoxicillin-clavulanic acid (4.88%). Among gram-negative bacteria, E. coli isolates showed a high resistance to ampicillin (30.64%), and a moderate resistance to amoxicillin-clavulanic acid (11.78%) and cefovecin (11.11%), antibiotics considered as first-line choices to treat UTIs in cats. Compared to 2020, the rate of E. coli isolates resistant to amoxicillin-clavulanic acid was lower in 2022 (IRR: 0.42; 95%; CI: 0.18-0.99). This study provides antibiograms of common feline urinary pathogens in Illinois that could aid veterinarians in their empirical UTI therapy choices. Requesting an antimicrobial susceptibility test when starting an empirical treatment could be beneficial to guide altered therapy to secure treatment success if the causative pathogens are resistant to the empirical antimicrobial choices.

Florfenicol urinary excretion and its potential for treating canine urinary tract infections

The canine urinary excretion of florfenicol was evaluated to explore its potential for treating urinary tract infections. Nine healthy male intact purpose-bred Beagles and four healthy client-owned dogs each received a single oral dose of florfenicol 20 mg/kg (300 mg/mL parenteral solution) with food. All voluntary urinations were collected for 12 h. Although florfenicol is reportedly bitter tasting, 7/9 Beagles and 4/4 client-owned dogs completely ingested the florfenicol and were enrolled; salivation (n = 1) and headshaking (n = 3) were observed. The last measured urine florfenicol concentrations were variable: Beagles (0.23-3.19 mcg/mL), Pug (3.01 mcg/mL) English Setter (21.29 mcg/mL), Greyhound (32.68 mcg/mL), and Standard Poodle (13.00 mcg/mL). Urine half-life was similar for the Beagles and the Pug, 0.75-1.39 h, whereas the half-life was 1.70-1.82 h for the English Setter, Greyhound, and Standard Poodle. Larger breed dogs exceeded 8 mcg/mL florfenicol (wild-type cutoff) in their urine at 12 h, whereas the Beagles and Pug had <8 mcg/mL; it is unclear if this is an individual, breed, or size difference. These data suggest oral florfenicol may need to be administered q6-12h for canine urinary tract infections, but further data are needed (more enrolled dogs, multiple-dose regimens) before considering clinical trials or breed-specific differences.