FIG 2.

Competitive interactions between S. aureus and other microbes. S. aureus exhibits antagonism toward P. aeruginosa, Streptococcus sp., and Lactobacillus sp. P. aeruginosa produces phenazine (PZ), hydrogen cyanide (HCN), quinolone oxidase (QO), and pyocyanin (PY), resulting in the respiratory blockage of S. aureus, which in turn leads to the formation of small-colony variants (SCVs). SCVs are more persistent and are resistant to antibiotics. Lactobacillus sp. and Streptococcus sp. inhibit the growth of S. aureus by producing hydrogen peroxide (H₂O₂). S. aureus produces staphyloxanthin and catalase, which neutralize the toxic effects of H₂O₂. Additionally, Lactobacillus spp. produce organic acids and bacteriocins that limit the growth of S. aureus. Certain S. aureus strains also produce bacteriocins such as staphylococcin Au 26, which in turn inhibit the growth of lactobacilli. Blocked arrows indicate antagonism, and arrows indicate survival strategies of S. aureus.