Characteristics of Dogs with Biofilm-Forming Escherichia Coli Urinary Tract Infections

Abstract

Background: Bacterial urinary tract infections (UTIs) are common in companion animals. Increasing awareness of biofilm-forming bacteria raises concern regarding the appropriate diagnosis, treatment, and prognosis of UTIs associated with these organisms.

Hypothesis/objectives: To (1) describe the population of dogs with UTIs associated with biofilm-forming Escherichia coli and (2) determine whether or not clinical differences exist between dogs with biofilm-forming E. coli UTIs and dogs with nonbiofilm-forming E. coli UTIs. We hypothesized that there would be no difference in the population characteristics, but that biofilm-formation would be more prevalent in dogs with chronic, complicated, and asymptomatic UTIs.

Animals: Seventy-six client-owned dogs with E. coli UTIs, divided into 2 groups based on the biofilm-forming capability of stored bacterial isolates as assessed by the crystal violet assay.

Methods: Retrospective cross-sectional study. Medical records of the affected dogs were reviewed and their population and infection characteristics were compared.

Results: Most (52.6%) E. coli isolates were capable of forming biofilms. Biofilm-forming E. coli had a lower likelihood (P < .001) of multidrug resistance than did nonbiofilm-forming E. coli. No statistically significant differences were identified between the population or infection characteristics of the 2 groups of dogs.

Conclusions and clinical importance: Escherichia coli isolated from canine urinary tracts are frequently capable of forming biofilms. Because no reliable clinical features allowed exclusion of biofilm formation, the potential for biofilm formation should be considered whenever E. coli UTI is diagnosed. The association of antibiotic resistance and biofilm potential may affect treatment of UTIs, but additional investigation is warranted.

Keywords: chronic urinary tract infection; crystal violet; multidrug resistance; symptomatic urinary tract infection.

Figure 1

Box‐and‐whiskers plots of population characteristics. Legend: Box‐and‐whiskers plot of (A) age (years), (B) BCS (9‐point scale), and (C) weight (kg) of all dogs (n = 76) in the study. The box represents the middle 50%, or IQR, while the bold horizontal line represents the median. Whiskers, the vertical lines above and below the box, show 1.5 times the IQR. Filled circles are outliers. Open circles represent each individual case. Abbreviations: BCS, body condition score; BF−, dogs with nonbiofilm‐forming E. coli isolates; BF+, dogs with biofilm‐forming E. coli isolates

Figure 2

Infection characteristics. Legend: Bars represent the proportion of isolates (n = 78) associated with the infection characteristics described on the x‐axis. Black bars represent nonbiofilm‐forming E. coli isolates, and white bars represent biofilm‐forming E. coli isolates. Error bars show the 95% confidence interval. Abbreviations: BF−, dogs with nonbiofilm‐forming E. coli isolates; BF+, dogs with biofilm‐forming E. coli isolates; MDR, multidrug resistance; chronic, dogs with chronic bacteriuria; LUTS, dogs with lower urinary tract signs. *Denotes statistical significance (P < .001)