The inhibitory effects of Staphylococcus aureus on the antibiotic susceptibility and virulence factors of Pseudomonas aeruginosa: A549 cell line model

Pseudomonas aeruginosa and Staphylococcus aureus often lead to serious lung infections. This study aimed to investigate the role of S. aureus in the expression of the beta-lactamase enzymes and virulence factors of P. aeruginosa in the polymicrobial infections of the respiratory tract. Biofilm and planktonic co-culture of P. aeruginosa and S. aureus were performed in the A549 cell line. Then, antibiotic resistance and virulence factors of P. aeruginosa were examined, and the expression of lasR, lasI, algD, mexR, and KPC genes were determined using qPCR. S.aureus decreased beta-lactam resistance but increased resistance to tobramycin in the biofilm condition. Furthermore, S.aureus showed a positive effect on reducing resistance to meropenem, doripenem, and tobramycin (except PA-2). Altough it was demonstrated that S.aureus reduced the viability of P. aeruginosa, particularly in the biofilm state, the pathogenicity of the recovered strains of P.aeruginosa increased. Moreover, the gene expression levels for lasR/I and algD were increased in biofilm conditions. The levels of lasI were more prominent in the virulent strain than the beta-lactamase producing strain. Furthermore, the expression of KPC was increased in all strains of P. aeruginosa. According to the findings of this study, S. aureus has an inhibitory effect in polymicrobial infections by suppressing the beta-lactamase genes and viability of P. aeruginosa. Also, it cooperates with the biofilm-producing P. aeruginosa strains to increase pathogenicity and resistance to tobramycin.