Subclinical bacteriuria is nonprogressive but persistent in dogs four years of age or older recruited from a small animal primary care setting

Objective: To evaluate clinical and microbial outcomes in dogs with untreated subclinical bacteriuria (SB) through longitudinal follow-up.

Methods: Between February 24, 2022, and July 7, 2023, healthy client-owned dogs ≥ 4 years old with no evidence of lower urinary tract signs (LUTS) were recruited for a longitudinal, prospective study. Phase 1 dogs with SB were followed for 28 days to document comorbidities and microbiological findings (ie, urinalysis, urine culture, and fimH gene in Escherichia coli isolates). Phase 1 participants enrolled in phase 2 were followed for at least an additional 120 days.

Results: The prevalence of SB was 11% (11 of 99), and all were female spayed. Of those with SB, 6 (55%) were followed for a median of 238 days; 91% (10 of 11) of phase 1 dogs and 67% (4 of 6) of phase 2 dogs had persistent bacteriuria, and 1 developed pyelonephritis 299 days after enrollment. Most dogs had E coli (8 of 11 [73%]), all of which contained the fimH gene. No change in antimicrobial susceptibility was noted during follow-up.

Conclusions: SB is generally nonprogressive and can persist for months after diagnosis. Patients with SB were more likely to be female, but no difference related to age, weight, or life stage was found. The presence of fimH, previously associated with biofilm, was negatively correlated with antimicrobial resistance.

Clinical relevance: For dogs with SB that are otherwise healthy, avoidance of systemic antimicrobials is warranted. For dogs with additional comorbidities, which might not be accompanied by, for example, pyelonephritis, or preclude the demonstration of LUTS, veterinarians should review the medical history and consider additional diagnostic testing.