Nanobacteria may be linked to testicular microlithiasis in infertility.

Testicular microlithiasis (TM) in infertility is an uncommon pathologic condition of unclear etiology that is characterized by calcium deposits within the seminiferous tubules. Nanobacteria (NB), as novel microorganisms mediating tissue calcification, have been discovered in some diseases. In this study, we hypothesized that NB may participate in the pathogenesis of TM, particularly in infertility. Seventeen infertility patients with TM detected by scrotal color Doppler ultrasonography and 17 infertility patients without TM as controls were enrolled in the study. The NB were isolated and cultured from semen samples and urine samples. After 3 to 6 weeks of culture, 10 of 17 (58.8%) semen samples and 2 urine samples from infertile patients with TM showed the growth of white granular microbes that firmly attached to the bottom of the culture flask and were visible to the naked eye. In the control group, only 1 of 17 (5.9%) semen samples from infertile patients without TM showed the growth of white granular microbes. The cultured microbes were identified by indirect immunofluorescent staining (IIFS), transmission electron microscopy (TEM), and 16s rRNA gene expression. IIFS and TEM revealed NB to be coccoid and 100 to 500 nm in diameter. The BLAST result revealed that the 16s rRNA gene sequence from the cultured microbes was 97% the same as that of the known NB. Our results showed that NB may be linked to the development of TM, which may provide a potential target for the diagnosis and treatment of infertility with TM.