A clinically relevant isolation of Gardnerella leopoldii guided with morphological and molecular evidences from a urinary tract infection case

Liangyou Chen ¹ Wei Weng ² Dan Li ³ Lingling Lu ^3* Shuo Li ^3,4*

• ¹ Department of Urology, Affiliated Jinhua Hospital, Zhejiang University School of Medicine, Jinhua, China
• ² Department of Diagnosis, The second Hospital of Jinhua, Jinhua, China
• ³ Zhejiang Key Laboratory of Digital Technology in Medical Diagnostics, Dian Diagnostics Group Co., Ltd., Hangzhou, Jiangsu Province, China
• ⁴ Precision Medicine Center, Affiliated Jinhua Hospital, Zhejiang University School of Medicine, Jinhua, China

The genus Gardnerella has been widely reported in the vaginal ecosystem and been considered as a covert pathogen of the urinary tract. However, Gardnerella vaginalis had been the only recognized species of the genus Gardnerella for decades. Cases about the clinical relevance of Gardnerella leopoldii have been rarely reported, which is crucial to fully understand various species in the genus Gardnerella.Case presentation: A 72-year-old female patient was admitted to the hospital with gross hematuria and complaints of waist soreness. Physical examinations including head, chest, and abdomen, and along with routine laboratory tests such as white blood cell count and proportion, liver function, and renal function, yielded normal results. However, the patient also exhibited significantly elevated serum C-reactive protein level and abnormal urinary test results, including positive occult blood, leukocyte esterase, and increased erythrocyte and leukocyte counts. To further evaluate the urinary system, computerized tomography urography (CTU) was performed. Results of CTU revealed multiple weakly enhanced foci in the right kidney, along with thickening of the right ureter, renal pelvis, calyces, and bladder walls. Based on the above findings, the initial diagnosis included hematuria, hydronephrosis and urinary tract infection (UTI). To identify the causative pathogens, comprehensive approaches combining microscopic morphology, Sanger sequencing, and metagenomic next-generation sequencing (mNGS) were conducted. Finally, both Mycobacterium tuberculosis and G. leopoldii were identified as the co-infecting etiological agents responsible for the patient's urinary tract infection. Conclusions: This case illustrates the first documented isolation of clinically relevant G. leopoldii guided by morphological and molecular evidence from a clinical urine sample. It highlights the potential of mNGS as a promising tool for the identification of previously unrecognized species and offers valuable insights for advancing the understanding of clinically relevant microorganisms.