Characterization of the Urogenital Microbiome in Miniature Schnauzers with and without Calcium Oxalate Urolithiasis

Calcium oxalate (CaOx) is an increasingly common, yet poorly understood, urolith affecting dogs. Humans with CaOx urolithiasis exhibit alterations of the urinary and urogenital microbiomes that might mediate stone formation. Detection of urogenital microbes associated with CaOx in dogs could inform disease pathophysiology. The objective of this study was to identify differences in the composition of the urogenital microbiome of Miniature Schnauzers with and without CaOx uroliths. Nineteen midstream, voided urine samples were included from Miniature Schnauzers with (n = 9) and without (n = 10) a history of CaOx urolithiasis. Microbial DNA was extracted from previously frozen urine samples and sequenced for the bacterial 16S rRNA V3-V4 hypervariable regions. Diversity and composition of microbial populations were compared between stone formers and controls. Alpha and beta diversity measures were similar between groups. Five individual bacterial taxa differed in abundance (indicator values > 0.5 and P for indicator value < .05): Acinetobacter, 2 Geobacillus variants, and Hydrogenophaga were overrepresented in the urine of stone formers, and Sphingopyxis was overrepresented in controls. Two distinct subtypes of urine microbial composition were observed, independent of stone status and other clinical variables. One of the bacterial taxon overrepresented in stone formers, Acinetobacter, is also associated with human CaOx urolithiasis. It is unknown whether the alterations in this taxon contribute to or are a consequence of stone formation. Two unique clusters of the microbiome were identified, independent of stone status, which may represent distinct urotypes present in Miniature Schnauzers.