Substantial overlap between symptomatic and asymptomatic genitourinary microbiota states.

BACKGROUND

The lack of a definition of urinary microbiome health convolutes diagnosis of urinary tract infections (UTIs), especially when non-traditional uropathogens or paucity of bacteria are recovered from symptomatic patients in routine standard-of-care urine tests. Here, we used shotgun metagenomic sequencing to characterize the microbial composition of asymptomatic volunteers in a set of 30 longitudinally collected urine specimens. Using permutation tests, we established a range of asymptomatic microbiota states, and use these to contextualize the microbiota of 122 urine specimens collected from patients with suspected UTIs diagnostically categorized by standard-of-care urinalysis within that range. Finally, we used a standard-of-care culture protocol to evaluate the efficiency of culture-based recovery of the urinary microbiota.

RESULTS

The majority of genitourinary microbiota in individals suspected to have UTI overlapped with the spectrum of asymptomatic microbiota states. Longitudinal characterization of the genitourinary microbiome in urine specimens collected from asymptomatic volunteers revealed fluctuations of microbial functions and taxonomy over time. White blood cell counts from urinalysis suggested that urine specimens categorized as 'insignificant', 'contaminated', or 'no-growth' by conventional culture methods frequently showed signs of urinary tract inflammation, but this inflammation is not associated with genitourinary microbiota dysbiosis. Comparison of directly sequenced urine specimens with standard-of-care culturing confirmed that culture-based diagnosis biases genitourinary microbiota recovery towards the traditional uropathogens Escherichia coli and Klebsiella pneumoniae.

CONCLUSION

Here, we utilize shotgun metagenomic sequencing to establish a baseline of asymptomatic genitourinary microbiota states. Using this baseline we establish substantial overlap between symptomatic and asymptomatic genitourinary microbiota states. Our results establish that bacterial presence alone does not explain the onset of clinical symptoms. Video Abstract.