(A) Minimum inhibitory concentrations (MIC) of the indicated antibiotics against S. felis C4. (B) Representative images of the dorsal skin of 8–10 week-old SKH1 mice 3 days post-challenge with live S. felis C4, S. pseudintermedius ST71 (S. pseud ST71) or S. felis ATCC (49168), inoculated at the indicated amounts. n = 2, per treatment group. (C–E) 5 × 107 CFU/cm2 of S. pseudintermedius ST71 was applied onto the back skin of C57BL/6 mice for 48 hr and challenged with TSB, S. felis C4 extract (1 mg) or live S. felis C4 (5 × 107 CFU/cm2) for 72 hr. Post-treatment, mouse back skin was photographed (C) and swabbed to enumerate S. pseudintermedius ST71 CFU on selective Baird-Parker egg yolk tellurite agar (D) or total staphylococci CFU on selective mannitol-salt agar plates (E). n = 3 for TSB and n = 4 for extract and S. felis C4. Error bars indicate SEM. One-way ANOVA with multiple comparisons (Dunnett’s correction) was performed. p values: *p < 0.05; (F–G) At day 0, 1 × 107 CFU of S. pseudintermedius ST71 was intradermally injected into the back skin of 8–10 week-old C57BL/6 mice and at 1 hr post-infection two inoculations of S. felis C4 extract (250 μg) or PBS/25 % DMSO control were injected adjacent to the infection site. (F) Representative images of S. pseudintermedius ST71-induced dermonecrosis over time after receiving control PBS/DMSO or S. felis C4 extract. (G) Quantification of lesion size (mm2) over time as measured by L x W of lesions. n = 4 for DMSO/PBS and n = 5 for extract. Error bars indicate SEM. A two-tailed, unpaired Student’s t-test was performed. p values: *p < 0.05; **p < 0.01; ***p < 0.001.
Figure 6—source data 1. Source data for Figure 6D and E (CFU counts on mouse back skin for S.p ST71 and total CoNS) and Figure 6G (measurements of lesion sizes over time in S. p ST71 infected skin).