| description |
Streptococcus pyogenes is a major cause of necrotizing fasciitis, a life-threatening subcutaneous soft-tissue infection. At the host infection site, the local environment and interaction between host and bacteria affect bacterial gene-expression profiles, but the S. pyogenes gene-expression pattern in necrotizing fasciitis remains unknown. In this study, we used a mouse model of necrotizing fasciitis and performed RNA-sequencing (RNA-seq) analysis of S. pyogenes M1T1 strain 5448 by using infected hindlimbs obtained at 24, 48, and 96 h post-infection. The RNA-seq analysis identified 483 bacterial genes whose expression was consistently altered in the infected hindlimbs as compared to their expression under in vitro conditions. The consistently enriched genes during infection included 306 genes encoding molecules involved in virulence, carbohydrate utilization, amino acid metabolism, trace-metal transport and vacuolar ATPase transport system. Surprisingly, drastic upregulation of 3 genes, encoding streptolysin S precursor (sagA), cysteine protease (speB), and secreted DNase (spd), was noted in the mouse model of necrotizing fasciitis (log2 fold-change values: >6.0, >9.4, and >7.1, respectively). Conversely, the consistently downregulated genes included 177 genes, containing genes associated with oxidative-stress response and cell division. These results suggest that S. pyogenes in necrotizing fasciitis changes its metabolism, decreases cell proliferation, and upregulates the expression of major toxins. Our findings could provide critical information for developing novel treatment strategies and vaccines for necrotizing fasciitis. |