Tissue distribution, renal pathology, and virulence-associated gene expression of Trueperella pyogenes in a mouse...

Trueperella pyogenes is an opportunistic pathogen that causes suppurative infections in a wide range of animal species; however, its in vivo pathogenesis and tissue distribution remain poorly defined. Therefore, we established a mouse infection model to investigate tissue dissemination, pathological changes, and tissue-associated virulence gene expression following T. pyogenes infection. Mice were intraperitoneally inoculated with a T. pyogenes isolate originating from a calf with diphtheria and monitored for 14 days post-infection (dpi). T. pyogenes was detected in all examined tissues, with the highest detection frequencies in the spleen and bladder. Notably, frequent bacterial detection in the bladder, together with progressive renal inflammatory lesions, suggests that the urinary tract may represent a potential site of bacterial localization during infection. Histopathological examination revealed a progression from acute suppurative inflammation to chronic inflammatory changes in the kidneys, whereas no remarkable lesions were observed in the lungs despite persistent bacterial detection. Infection also induced spleen enlargement and a transient reduction in CD8⁺ T cells at 10 dpi (p = 0.028). Expression of virulence-associated genes demonstrated tissue-specific patterns, with consistently higher expression of fimA than plo across tissues. In particular, elevated fimA expression in the spleen and heart (p < 0.001 for both) may contribute to bacterial persistence and tissue dissemination. Overall, T. pyogenes infection in mice is characterized by systemic tissue dissemination, urinary tract localization, progressive renal inflammation, and tissue-specific virulence gene expression. These findings provide additional insights into the in vivo distribution and organ-associated pathogenic features of T. pyogenes.