Geographic Patterns of Antimicrobial Resistance in Companion Animal Urinary Tract Infections in Europe

In an analysis of bacteria isolated from canine and feline urinary tract infections (UTIs) in Europe, antimicrobial resistance was generally more prevalent in southern Europe than in northern Europe. Stricter regulations on veterinary antimicrobial use in certain countries may explain the difference, according to the authors.

Antimicrobial resistance in companion animals is a public health problem as well as a challenge for veterinary practitioners, say the authors. “…[T]hese pathogens may be zoonotic and companion animals may play a role in the spread of resistant bacteria due to their close contact to humans,” they write. “This work…reinforces the need for strategies aiming to reduce resistance.”

The multicenter retrospective study included data from 15,097 positive urine cultures in dogs and 5963 positive urine cultures in cats, yielding 22,256 bacterial isolates. The data were collected by 16 veterinary microbiology laboratories in 14 countries between 2008 and 2013. Susceptibility testing methods varied from country to country.

The most common isolate in canine and feline samples was Escherichia coli, accounting for over half of all bacteria found in urine cultures. The next most common isolates in dogs were Proteus and Staphylococcus species; in cats, the next most common were Staphylococcus and Enterococcus species.

The investigators examined the resistance patterns of E. coli and Proteus species within individual countries from 2012 to 2013. In general, northern countries (Denmark and Sweden) had the lowest overall prevalence of antimicrobial resistance; southern countries (Italy, Greece, Portugal, and Spain) had the highest.

The low prevalence of resistance in certain countries is probably due to strict regulations on antimicrobial prescribing for companion animals and surveillance of antibacterial resistance, say the authors. “In light of the present results, such strategies could be useful in aiming the reduction of antimicrobial resistance in the Southern countries,” they write.

Other notable results include the following:

• Amoxicillin-clavulanate: Nearly half of E. coli and half of Proteus isolates from Portugal were resistant to amoxicillin-clavulanate. In contrast, fewer than 3% of E. coli isolates from Denmark were resistant to amoxicillin-clavulanate. The authors recommend further investigation to determine whether amoxicillin-clavulanate is an appropriate empiric antibiotic choice for dogs and cats with UTIs in southern Europe.
• Third-generation cephalosporins: The percentages of E. coli isolates resistant to third-generation cephalosporins were highest in Portugal, Italy, and Spain. One-third of Proteus isolates from Portugal were resistant to third-generation cephalosporins. Northern countries had the lowest percentages of resistant E. coli and Proteus species. The authors note that “prudent use” of third-generation cephalosporins is crucial because these drugs are also of great importance in human medicine.
• Fluoroquinolones: The percentages of E. coli, Proteus species, and Staphylococcus species resistant to fluoroquinolones were higher in this study than in previous reports. This result is troubling, say the authors, because fluoroquinolones are typically used as first-line treatment for pyelonephritis and should be reserved as a second choice for other infections.
• Multidrug resistance: Southern European countries had the highest percentages of E. coli resistant to multiple antimicrobials.
• The incidence of antimicrobial-resistant E. coli decreased over time in many countries. In some countries, the percentage of resistant E. coli isolates decreased for some antimicrobials but increased for others.

The authors note several study limitations. The differences in susceptibility testing methods among the laboratories complicated comparisons between countries. Because the study was retrospective, no information about patients’ prior antimicrobial treatment was available. Samples submitted for testing were more likely to come from patients with complicated UTIs than from those with uncomplicated UTIs that were treated empirically; this could have caused a bias toward resistance.

The authors suggest that a European surveillance network should collate clinical and antimicrobial resistance data in veterinary patients, with the goal of developing evidence-based antimicrobial use guidelines. They recommend that antimicrobial resistance be monitored in Europe in companion animals, as it is in food animals, to control the spread of resistance.

Dr. Laurie Anne Walden received her doctorate in veterinary medicine from North Carolina State University. After an internship in small animal medicine and surgery at Auburn University, she returned to North Carolina, where she has been in small animal primary care practice for over 20 years. Dr. Walden is also a board-certified editor in the life sciences and owner of Walden Medical Writing, LLC. She works as a full-time freelance medical writer and editor and continues to see patients a few days each month.