Comparison of canine urinary bacterial population in calcium oxalate urolithiasis and healthy conditions

Abstract

Urolithiasis is one of the most common lower urinary tract diseases in dogs. Struvite is the most canine uroliths reported, and the second reported is calcium oxalate (CaOx). However, the proportion of CaOx urolithiasis tends to be increased. CaOx urolithiasis has high incidence of recurrence after the treatment and the pathogenesis of the stone formation is uncleared. Recent studies revealed that oxalate degrader bacteria in the gastrointestinal tract has important roles in CaOx stone formation but no research has been done to study the composition and the role of microbiome in the urinary tract of dogs with CaOx urolithiasis. This study has purpose to characterize the urinary bacterial population in urinary bladder of dogs with CaOx urolithiasis and to compare the difference of microbiome in urinary bladder of dogs with healthy condition and CaOx urolithiasis. Urine samples were collected by cystocentesis from 10 healthy female, 9 healthy male, 6 CaOx urolithiasis female, and 7 CaOx urolithiasis male dogs undergoing neutering and cystotomy procedures. Urine samples were used for urinalysis, urine culture, and 16S rRNA amplicon sequencing by using next generation sequencer (miseq). The V3-V4 region of the 16S rRNA bacterial gene was amplified and compared for operational taxonomic units (OTU) data and relative abundance for both urine samples. We found that the urinary microbiota from CaOx urolithiasis dog had significantly higher abundance and evenness compared to the healthy dogs (p-value = 0.0035), with no significant found difference between sex. We also found significant higher amount of the microbes in CaOx urolithiasis group than another group which are family Caulobacteraceae, class Alphaproteobacteria, and family Oxalobacteraceae genus Ralstonia. These microbes are related with the oxalotrophic bacteria, oxalate degrader microorganism lives in gastrointestinal tract that has a role in CaOx stone formation. In conclusion, while recognizing the limitations of the diagnosis and treatment, this finding may lead to more accurate diagnosis, alternative treatment, or even though prevention methods in the future.