Prior studies found evidence that the gene SA618 is important in resistance of S. aureus to the antibiotic Tunicamycin; however, over-expression of the gene SA1798 was shown to negate the effect of losing SA618. In this study, the role of SA1798 was investigated through UPLC-MS and MALDI analysis of muropeptides and by generation of a single nucleotide polymorphism in the promoter of SA1798 that results in over-expression of the gene and reduced antibiotic susceptibility.