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

In the Literature

Kern ZT, Jacob ME, Gilbertie JM, Vaden SL, Lyle SK. Characteristics of dogs with biofilm-forming Escherichia coli urinary tract infections. J Vet Intern Med. 2018;32(5):1645-1651.

The Research …

Some strains of Escherichia coli have the ability to form biofilms, either in vivo or in vitro. Biofilm formation can lead to antibiotic resistance or tolerance and can be associated with complicated and/or recurrent UTIs in humans. The role of biofilms in UTIs in dogs, however, is not well-defined.

In this study of UTIs caused by E coli in dogs, 52.6% of the 78 E coli isolates tested had biofilm-forming capability. There were no differences in breed, age, sex, or body condition among dogs with biofilm-forming and non-biofilm–forming E coli, and presence of lower urinary tract signs was similar between groups (biofilm-forming, 34%; non-biofilm–forming, 32%). Although previous studies have typically shown associations between biofilm-forming bacteria and multidrug resistance, this study found biofilm-forming E coli to be less likely to exhibit multidrug resistance than were non-biofilm–forming E coli. It is important to note that susceptibility testing is performed on bacteria in a planktonic (vs biofilm) state, so antibiotic tolerance resulting from biofilm formation would not be included in a susceptibility report.

Results from this study did not address whether testing for biofilm-forming capability in E coli UTI cases is warranted or whether the presence of biofilm-forming E coli affects the patient’s ability to clear infection. It is unknown whether E coli that form biofilms in laboratory settings also do so in patients. In addition, even if E coli do form biofilms in a patient, it is unknown whether this will impact antibiotic susceptibility in the patient. If there is difficulty in clearing a UTI, culture and susceptibility testing should be performed, as the bacteria may still be susceptible to less-restricted antibiotics (eg, amoxicillin–clavulanic acid, first-generation cephalosporin). This is also true of biofilms that may form on a urolith in the bladder. In cases in which the patient has an implant or urolith, both of which are not perfused with blood, bacteria may be protected in a biofilm from the action of antibiotics in the urine; thus, implant and/or urolith removal may be the best option.

… The Takeaways

Key pearls to put into practice:

• Approximately half of E coli found in the urinary tract have the capability to form a biofilm.

• The ability to form a biofilm does not necessarily mean the bacteria will be resistant to commonly used antibiotics.

• Patients that may have an E coli biofilm on a urolith or urinary implant may require removal of the stone or replacement of the implant to eliminate the infection.