Subclinical bacteriuria — a hidden diagnosis for both dogs and veterinarians

Background

Urinary tract infections (UTIs) are relatively common in dogs and can cause discomfort and suffering for both the animal and its owner. Historically, urine was considered sterile, and the presence of high numbers of bacteria was generally interpreted as evidence of infection. However, recent research has shown that bacteria can be detected in the urine of healthy dogs without clinical signs of disease. This condition is referred to as subclinical bacteriuria. Because UTIs are among the conditions frequently treated with antibiotics in dogs, improving knowledge of subclinical bacteriuria is essential to ensure that antibiotics are used appropriately and are not administered to dogs that carry bacteria but show no signs of illness.

Project overview

Significant knowledge gaps remain regarding subclinical bacteriuria in dogs. To date, only a limited number of scientific studies have investigated this condition, and none have been conducted in Sweden.

In this study, we will begin with a screening phase using bacteriological analysis of spontaneously collected urine samples from dogs without clinical signs of urinary tract infection. The samples will be analysed for bacterial growth to determine (i) the prevalence and extent of subclinical bacteriuria in Swedish dogs and (ii) whether sex (female or male) is associated with its occurrence.

Dogs with suspected subclinical bacteriuria, defined as bacterial growth in conventional urine cultures, will undergo further investigation. Urine samples will be collected directly from the bladder by cystocentesis to (iii) quantify bacterial load and (iv) determine whether bacteria persist over time or represent temporary colonization. Bacterial isolates will be identified to species level using MALDI-TOF MS and stored at −70°C for further analysis. Whole-genome sequencing will be performed, and the bacterial genomes will be compared with those of bacterial species isolated from dogs with clinical urinary tract infections.

Objectives

The aim of this project is to improve understanding of the prevalence of subclinical bacteriuria in dogs in Sweden and determine whether dogs can carry bacteria in their urine over extended periods or whether bacterial presence is transient.

In addition, we will also investigate which bacterial species are most associated with subclinical bacteriuria and whether these species correspond to those identified in dogs with symptomatic urinary tract infections. Furthermore, genomic analysis of bacteria from subclinical bacteriuria will provide insight into the possible presence or absence of virulence factors that may influence their ability to cause disease.