New Evidence and Insights on Dalbavancin and Wound Healing in a Mouse Model of Skin Infection

Abstract

Dalbavancin is an effective antibiotic that is widely used to treat skin infection. Our aim was to determine the effect of dalbavancin administration on wound healing compared to that of vancomycin and to elucidate if epidermal growth factor receptor (EGFR), matrix metalloproteinase 1 (MMP-1), MMP-9, and vascular endothelial growth factor (VEGF) could be involved in its therapeutic mechanism. A mouse model of methicillin-resistant Staphylococcus aureus (MRSA) skin infection was established. Mice were treated daily with vancomycin (10 mg/kg) and weekly with dalbavancin at day 1 (20 mg/kg) and day 8 (10 mg/kg). After 14 days, wounds were excised, and bacterial counts were performed. Wound healing was assessed by histological and immunohistochemical staining, followed by protein extraction and immunoblotting. Our microbiological results confirmed that both dalbavancin and vancomycin are effective in reducing the bacterial load in wounds. The dalbavancin group showed a strong effect compared with infected untreated animals and the vancomycin-treated group. The wounds treated with dalbavancin showed robust epidermal coverage with reconstitution of the regular and keratinized epidermal lining and well-organized granulation tissue with numerous blood vessels, although slightly less than that in the uninfected group. While in the vancomycin-treated group the epithelium appeared, in general, still hypertrophic, the granulation tissue appeared even less organized. We observed elevated EGFR and VEGF expression in both treated groups, although it was higher in dalbavancin-treated mice. MMP-1 and MMP-9 were decreased in uninfected tissue and in both treated tissues compared with untreated infected wounds. This study showed faster healing with dalbavancin treatment that might be associated with higher EGFR and VEGF levels.

Keywords: EGFR; MMP-1; MMP-9; VEGF; dalbavancin; wound healing.

FIG 1

Bacterial counts of excised wound. Counts are expressed as log CFU/ml. The limit of detection for this method was approximately 10 CFU/ml. *, P < 0.05 (compared to the infected but not treated group).

FIG 2

Representative images of hematoxylin- and eosin-stained histological sections of wound healing tissues from uninfected mice, infected mice treated with dalbavancin or vancomycin, and infected untreated mice on day 14 after injury. Wound healing was still incomplete in the untreated groups, but both treated groups exhibited good reepithelialization; in particular, the wounds treated with dalbavancin showed robust epidermal coverage and well-organized granulation tissue (original magnification, ×100).

FIG 3

Analysis of the expression of EGFR, MMP-1, MMP-9, and VEGF. Western blot and densitometric analyses of EGFR, MMP-1, MMP-9, and VEGF (a representative of the three performed experiments). Densitometric analyses of the immunoreactive bands are quantified as the ratio between bands relative to EGFR, VEGF, MMP-1, MMP-9, and glyceraldehyde-3-phosphate dehydrogenase (GAPDH) in corresponding samples, given in arbitrary units. Data are expressed as mean ± SD from analyses performed on uninfected, untreated infected, infected treated with vancomycin, and infected treated with dalbavancin tissue samples. *P < 0.05 for infected treated with dalbavancin versus uninfected, untreated infected, and infected treated with vancomycin groups. **P < 0.05 for untreated infected versus uninfected, infected treated with dalbavancin, and infected treated with vancomycin.