LTB₄ acts synergistically with mupirocin to increase MRSA clearance.

(A) Infection area measured every other day for 9 days post infection in WT mice infected with MRSA, s.c., and treated topically daily with vehicle-control ointment, 0.1% mupirocin ointment, LTB4 ointment, or mupirocin + LTB4 combination ointment. B) Bacterial load determined by CFU measured in the skin biopsy homogenates from mice treated as in (A) and collected at day 9 post-infection. C) Top: Representative bioluminescent MRSA detected in mice treated as in (A) using the in vivo animal imaging (IVIS Spectrum) detection system for the skin. Bottom: Bacterial load of bioluminescent MRSA in the skin of mice treated as in (A) using representative planar bioluminescent imaging (n = 5–6 mice/group). D) H&E stains from mice treated as in (A) and biopsies collected at day 1 post-MRSA skin infection. 40 X magnification and the white dotted lines indicate an abscess edge. E) (left) Masson’s trichrome blue staining from mice infected and treated with vehicle, LTB4, and LTB4 plus mupirocin for 24 h. The top is 40 X, the middle is 100 X and bottom is 400 X magnification. (right) The thickness of Masson’s trichrome blue positive layer surrounding the abscess was measured with ImageJ software as described in the Material and Methods. Data are the mean ± SEM of 4–5 mice from 1–2 experiments. *p < 0.05 vs. vehicle. **** p < 0.001 vs. vehicle.