Figure 7.

Resistance of Staphylococcus aureus to phagolysosome contents. The bacteria S. aureus modifies the composition of its cell wall to resist the action of lysozyme (206, 207) and alters the composition of its membrane, with l-lysine and lipoteichoic acids, to reduce the negative charge of the membrane (209, 210); thus resisting antimicrobial peptides, such as the cathelicidin LL-37. Also, it secretes staphylokinase and aureolysin to block α-defensins and LL-37, respectively (208, 211). In addition, S. aureus has the golden pigment staphyloxanthin (Sx), which works as an antioxidant (212), two super oxide dismutases (Sod) (213), and a catalase (214, 215) that together protect against reactive oxygen species. In addition, flavohemoglobin functions as an NO^⋅ scavenger (216, 217). The bacterial urease catalyzes the hydrolysis of urea to form ammonia, resulting in pH neutralization (218). Finally, S. aureus produces siderophores (SA) (219, 220) that trap enough Fe²⁺ to allow bacterial survival.