Urinary tract infections (UTI) are frequently seen in small animal practice. They are estimated to affect up to 5% of all dogs, but are far more common in female and older dogs with diabetes.
Signs of a UTI include diffi culty urinating, bloody or cloudy urine, increased urinary frequency along with decreased volume, accidents in the home, strong odor, vomiting, lethargy and increased water consumption. UTIs are caused by bacteria, with Escherichia coli (E.coli) being the most common. Other bacteria implicated in UTIs include Enterococcus, Klebsiella, Staphylococcus pseudintermedius and Pseudomonas.
Antibiotics are commonly prescribed for UTIs, and include cephalosporins, aminoglycosides, tetracyclines, fluoroquinolones and chloramphenicols. This has unfortunately resulted in increased antibiotic resistance among a variety of canine isolates, including E.coli.
Complicating the issue is that many UTI bacteria are present as a biofilm. A biofilm is a community of bacteria surrounded by a protective extracellular polymeric matrix consisting of a variety of compounds, including polysaccharides and glycoproteins. The biofilm matrix provides a physical barrier that protects the bacteria from the effects of antibiotics as well as the host immune system. The matrix is also porous enough to allow for the exchange of fluids and nutrients, resulting in an ideal environment for bacteria to thrive. Several studies have shown that the antibiotic-sensitivity profile of biofilm bacteria is very different than that of non-biofilm (planktonic) bacteria. In fact, biofilm bacteria may be more than 1,000 times more resistant to antibiotics than planktonic bacteria.
Traditional antibiotic culture and sensitivity testing of UTIs involves culturing a urine sample and exposing the resulting bacteria to a variety of antibiotics. A problem with this approach is that these bacteria are not grown as a biofilm. As a result, the test population does not accurately refl ect the form of bacteria in the patient, and incorrect antibiotic sensitivity profiles are often obtained. In addition to being ineffective, continued use of the incorrect antibiotic promotes widespread antibiotic-resistance in bacteria.
The BecSCREEN assay has been developed to determine antibiotic-sensitivity profiles specifically for biofilm bacteria. In this assay, the bacteria are first grown as a biofilm and then exposed to a variety of antibiotics and concentrations. The end result is a test that determines the antibiotic sensitivity of the bacteria as it would naturally exist in the UTI. This approach may allow for a more accurate antibiotic sensitivity profile and more effective treatment. Additionally, by treating the infection with the proper antibiotics, the possibility of antibiotic-resistant strains emerging is reduced.
As we learn more about UTIs and the dangers of acquired antibiotic resistance, the need for assays that more accurately test the effectiveness of antibiotics on bacteria as they naturally appear becomes obvious, and provides us with better treatment and improved quality of life for our patients.