Untargeted lipidomic differences between clinical strains of methicillin-sensitive and methicillin-resistant Staphylococcus aureus

Background Staphylococcus aureus is a common cause of infectious diseases in humans. It has become resistant to many antibacterial agents making management of infections difficult. A better understanding of differences among S. aureus strains that are sensitive and resistant to antibiotics may offer insights into the resistant phenotype and identify new antimicrobial targets. This study aimed at comparing general differences in lipid profiles among clinical strains of S. aureus sensitive and resistant to antibiotics. The cell wall thickness and cell surface charge were also compared. Methods Five methicillin sensitive (MSSA) and five methicillin resistant (MRSA) S. aureus strains were compared both individually and as MSSA and MRSA groups in the absence of antibiotics. Lipids were compared by ultra-performance liquid chromatography-mass spectrometry, cell wall thickness was compared by scanning transmission electron microscopy and whole-cell surface charge was compared using a cytochrome c binding assay. Results Twenty-two lipid species were identified in all ten strains of S. aureus. The abundance of three lipid species (two lysyl-phosphatidylglycerol and one diglycosyldiacylglycerol) were found to be different between MSSA and MRSA. Differences in cell wall thickness were identified between strains but not between MSSA and MRSA. No difference in whole-cell surface charge was observed between MSSA and MRSA. Conclusion This study shows differences in membrane lipids between antibiotic sensitive and antibiotic resistant clinical strains of S aureus that may affect resistance mechanisms related to cell membrane structure and fluidity. Further research on these differences may identify new drug targets against resistant strains.