Short- and Long-term Cure Rates of Short-duration Trimethoprim-sulfamethoxazole Treatment in Female Dogs with Uncomplicated Bacterial Cystitis

Background: Long-duration beta-lactam antibiotics are used for empirical treatment in female dogs with uncomplicated bacterial cystitis. However, women with bacterial cystitis are treated with short-duration potentiated sulfonamides because longer courses of beta-lactams result in lower cure and higher recurrence rates.

Hypothesis/objectives: Short-duration potentiated sulfonamide treatment is more efficacious than long-duration beta-lactam treatment in achieving clinical and microbiological cures in female dogs with uncomplicated bacterial cystitis.

Animals: Thirty-eight client-owned female dogs.

Methods: Randomized, double-blinded, placebo-controlled clinical trial. Dogs were treated with TMP-SMX (15 mg/kg PO q12h for 3 days followed by a placebo capsule PO q12h for 7 days; Group SDS; n = 20) or cephalexin (20 mg/kg PO q12h for 10 days; Group LDBL; n = 18). Dogs were monitored for clinical and microbiological cure during treatment and at short- and long-term follow-up.

Results: No statistically significant differences were found between treatment groups in clinical cure rates after 3 days of treatment (89% SDS, 94% LDBL; P = 1.00) and 4 days (85% SDS, 72% LDBL; P = .44) or >30 days (50% SDS, 65% LDBL; P = .50) after conclusion of treatment or in microbiological cure rates 4 days (59% SDS, 36% LDBL; P = .44) or >30 days (44% SDS, 20% LDBL; P = .40) after conclusion of treatment.

Conclusions And Clinical Importance: We did not identify a difference in cure rates between short-duration sulfonamide and long-duration beta-lactam treatments in female dogs with uncomplicated cystitis. Long-term cure rates in both treatment groups were low. In some female dogs, "uncomplicated" bacterial cystitis may be more complicated than previously recognized.