Zinc sulfate acts as an efflux pump inhibitor on Pseudomonas aeruginosa clinical isolates

Efflux pumps in Pseudomonas aeruginosa play an important role in decreasing the bacterium's antibiotic susceptibility. This study aimed to identify P. aeruginosa efflux pumps and examine the effect of Zinc sulfate on these pumps. This study was conducted on 104 P. aeruginosa clinical isolates collected from different types of specimens. The antimicrobial susceptibility pattern of all isolates was examined by disc diffusion and microdilution methods. A Cartwheel test was done for phenotypic detection of P. aeruginosa efflux pumps in the presence and absence of zinc sulfate. The expression of efflux pumps encoding genes and their regulators in the presence and absence of zinc sulfate was measured using real-time reverse transcriptase PCR. A high rate of multidrug-resistant (MDR) pattern was observed among the tested isolates (55.7%). Combining different antibiotics with Zinc sulfate exhibited synergistic effects against most of the studied isolates. The addition of sub-inhibitory concentrations of Zinc sulfate to the cartwheel test was found to inhibit efflux pump activity in all tested isolates. The expression of the positive regulator gene, mexT, was significantly decreased. Additionally, Zinc sulfate significantly upregulated the expression of the mexR gene (P-value < 0.05), a negative regulator of the MexAB-OprM efflux pump. Zinc sulfate demonstrated a strong antimicrobial effect against P. aeruginosa clinical isolates. We recommend the use of Zinc sulfate as an antibiotic adjuvant and efflux pump inhibitor in the treatment of P. aeruginosa infections to enhance the bacterium's susceptibility to antimicrobial agents.