Short- and long-term cure rates of short-duration trimethoprim-sulfamethoxazole treatment in female dogs with uncomplicated bacterial cystitis

Abstract

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.

Keywords: Beta-lactam; Cephalexin; Lower urinary tract infection; Sulfonamide.

Figure 1

Allocation of treatment groups for female dogs treated for bacterial cystitis with SDS treatment versus long‐duration beta‐lactam treatment. Lines with arrows indicate progression of dogs that entered the study, clinically responded to treatment, and did not have a recurrence of clinical signs. Lines with terminal ends indicate when dogs were excluded or withdrawn from the study. SDS, short‐duration sulfonamide treatment; LDBL, long‐duration beta‐lactam treatment; n, number of dogs in group.

Figure 2

Timeline of study events for female dogs treated for bacterial cystitis with SDS treatment versus long‐duration beta‐lactam treatment. Numbers correspond to study day; day 0 = enrollment and start of treatment, day 3 = completion of SDS treatment, day 10 = completion of LDBL treatment. Boxes denote duration of each treatment; open box = duration of SDS treatment, diagonal hatched box = duration of LDBL treatment. Symbols above the line correspond to SDS group events. Symbols below the line correspond to LDBL group events. Single‐headed arrows represent short‐term follow‐up time point for each treatment. Double‐headed arrows represent long‐term follow‐up time point for each treatment. Each star marks an individual dog's time point of recurrence of clinical signs in the SDS group; diamonds mark the same for dogs in the LDBL group. SDS, short‐duration sulfonamide treatment; LDBL, long‐duration beta‐lactam treatment.