FIG 1.

Features of mouse model of necrotizing fasciitis and workflow of bacterial RNA isolation. (A) Representative images of infected hindlimbs after inoculation with S. pyogenes M1T1 strain 5448. (B) Histopathological features of mouse model of necrotizing fasciitis. Hematoxylin and eosin staining of infected lesions at the indicated time points is shown, with higher-magnification images of the selected areas of the same sections also presented. At 24 h after infection, skin showed erosion of the epidermis and edematous thickening of the dermis (vertical bracket), as well as sparse inflammatory cell infiltration. At 24 and 48 h after infection, marked necrosis (asterisks) was observed, as the bacteria were primarily concentrated along the major fascial planes (arrows) in infected deep soft tissue. At 96 h after infection, sufficient inflammatory cell infiltration and elimination of pus (red arrows) from infected hindlimbs were observed. (C) Workflow of bacterial RNA isolation. Tissues were lysed with 1.4-mm silica spheres, and the mouse RNA fraction was removed after centrifugation. Pellets next were lysed with 0.1-mm silica spheres and centrifuged to obtain the bacterial RNA fraction. (D) Representative bioanalyzer profile of total RNA isolated from an infected hindlimb. 16S and 23S, bacterial rRNA peaks; 18S and 28S, mouse rRNA peaks. FU, fluorescence units.