Application of PEG-PCL-MP1 nanoparticle treatment for MRSA infection. a–d Skin infection. n = 5 mice/group, except PBS and MRSA + PEG-PCL control groups, n = 2. Two abscesses per mouse were produced. a Abscess sizes measured 22 h post-infection with 1 × 108 CFU MRSA (ST59) and the indicated treatment. b Abscess pictures. c, d Levels of cytokine gene expression in 22 h-abscesses determined by qRT-PCR. e High-dose systemic infection (sepsis), survival curves. Animals (n = 8/group) received 5 × 107 CFU MRSA (ST59) and the indicated treatment (3 mg/kg at 1 and 24 h). Analysis is by log-rank (Mantel-Cox) tests of the respective curves versus the MRSA curve. f–h Low-dose systemic infection (bacteremia). Animals (n = 6/group) received 1 × 107 CFU MRSA (ST59) and the indicated treatment. Animals were sacrificed 48 h post-infection. f Macroscopic analyses of livers and kidneys. Representative organs are shown. g Histopathological analysis of liver and kidney tissues. Representative pictures are shown. Arrows indicate tissue necrosis (yellow), hemorrhage (blue) and massive infiltration of inflammatory cells (black). h Bacterial load in the kidneys. a, c, d, h Statistical analysis is by Kruskal-Wallis tests and Dunn’s post-tests. Error bars show the mean ± SD.