Dina Al Nahhas (Alghero / IT), Salvatore Pisanu (Alghero / IT), Priscila Guerra (Sassari / DK), John Elmerdahl Olsen (Sassari / DK), Sergio Uzzau (Sassari / IT), Daniela Pagnozzi (Alghero / IT)
Objectives
Skin infections by methicillin-resistant Staphylococcus aureus (MRSA) present significant challenges due to their virulence and antibiotic resistance. This study aims to characterize the proteome variation of S. aureus during skin infection to identify new therapeutic targets.
Methods
Using in vivo (mouse model) and 3D in vitro skin models, we studied the proteome of S. aureus strains ST398 and JE2 (USA300) during skin infection. Mice were infected with 107 CFU mid-exponential phase cultures of MRSA onto a skin lesion by scrapping the dorsal back part, and skin samples were collected at 2- and 4- days post-infection for bacterial count and protein extraction. The 3D in vitro model, simulating human skin, was infected with 108 CFU of the same MRSA strains. After 2 days, we collected and extracted proteins from the tissues for analysis via shotgun proteomics, employing a Q-Exactive mass spectrometer. The data from this analysis were processed using SEQUEST-HT in Proteome Discoverer software. We applied a TMT labeling approach for the in vivo model and a label-free (LFQ) approach for the in vitro model.
Results and conclusion
KEGG mapping tool identified pathways involved in infection in both models, including glycolysis and gluconeogenesis, pentose phosphate pathway, and pyruvate metabolism, while glycine serine and threonine metabolism pathway was seen solely in the in vivo model. In addition, we attempted to understand strain-specific adaptations to the infection, highlighting an increase in the arginine biosynthesis pathway observed in JE2 in both tissue models, along with differences in S. aureus infection protein expression between the two strains, such as the upregulation of femX and femB genes in JE2 which are involved in peptidoglycan biosynthesis.
This research enhances our understanding of protein expression levels during skin infection. By broadening our comprehension of Staphylococcus aureus biology, our work paves the way for developing targeted therapeutic interventions, thereby offering a meaningful contribution to the fight against antimicrobial resistance