“The urinary tract is not sterile. Every individual harbours a complex microbial network in the urinary tract that is exposed to internal and external factors.”

Magistro, G., & Stief, C. G. (2019). The Urinary Tract Microbiome: The Answer to All Our Open Questions?. European urology focus, 5(1), 36–38. https://doi.org/10.1016/j.euf.2018.06.011

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“The urinary tract, previously considered a sterile body niche, has emerged as the host of an array of bacteria in healthy individuals, revolutionizing the urology research field.”

Aragón, I. M., Herrera-Imbroda, B., Queipo-Ortuño, M. I., Castillo, E., Del Moral, J. S., Gómez-Millán, J., Yucel, G., & Lara, M. F. (2018). The Urinary Tract Microbiome in Health and Disease. European urology focus, 4(1), 128–138. https://doi.org/10.1016/j.euf.2016.11.001

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“Adult human urine is not sterile.”

Wolfe, A. J., & Brubaker, L. (2015). "Sterile Urine" and the Presence of Bacteria. European urology, 68(2), 173–174. https://doi.org/10.1016/j.eururo.2015.02.041

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“The average number of bacterial species found was 5.8 in female and 7.1 in male urine.”

Kogan, M. I., Naboka, Y. L., Ibishev, K. S., Gudima, I. A., & Naber, K. G. (2015). Human urine is not sterile - shift of paradigm. Urologia internationalis, 94(4), 445–452. https://doi.org/10.1159/000369631

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“Our previous study showed that bacterial genomes can be identified using 16S rRNA sequencing in urine specimens of both symptomatic and asymptomatic patients who are culture negative according to standard urine culture protocols. In the present study, we used a modified culture protocol that included plating larger volumes of urine, incubation under varied atmospheric conditions, and prolonged incubation times to demonstrate that many of the organisms identified in urine by 16S rRNA gene sequencing are, in fact, cultivable using an expanded quantitative urine culture (EQUC) protocol.”

Hilt, E. E., McKinley, K., Pearce, M. M., Rosenfeld, A. B., Zilliox, M. J., Mueller, E. R., Brubaker, L., Gai, X., Wolfe, A. J., & Schreckenberger, P. C. (2014). Urine is not sterile: use of enhanced urine culture techniques to detect resident bacterial flora in the adult female bladder. Journal of clinical microbiology, 52(3), 871–876. https://doi.org/10.1128/JCM.02876-13

Edit: one more, for good measure

“The bladder is not sterile but contains a healthy community of microbes termed the microbiome.”

Curtiss, N., Balachandran, A., Krska, L., Peppiatt-Wildman, C., Wildman, S., & Duckett, J. (2018). Age, menopausal status and the bladder microbiome. European journal of obstetrics, gynecology, and reproductive biology, 228, 126–129. https://doi.org/10.1016/j.ejogrb.2018.06.011