Emerging Biocide Resistance in Staphylococcus aureus: Cross-Source Insights and Public Health Implications

Background Staphylococcus aureus causes numerous clinical infections. This study aimed to investigate the susceptibility of 553 S. aureus isolates collected from patients, healthy carriers, retail foods, and wastewater in Ardabil, Iran, to common antimicrobial biocides, including triclosan (TCS), chlorhexidine digluconate (CHDG), benzalkonium chloride (BZC), and formaldehyde (FOR). Additionally, the presence of Biocide Tolerance-Associated (BTA) genes was examined. Methods. The Minimum Inhibitory Concentration (MIC) of biocides was determined using the agar dilution technique. Concurrently, a polymerase chain reaction (PCR) was used to detect the BTA genes. Results. In the current study, MIC ₉₀ for TCS, CHDG, BZC, and FOR were 1 µg/ml, 1 µg/ml, 2 µg/ml, and 128 µg/ml, respectively, for total isolates. The MIC ₉₀ for TCS, CHDG, and BZC in clinical isolates was double the MIC ₉₀ of total isolates. The BTA genes, norA , mdeA , mepA , sepA , qacA/B , qacC , qacD , qacG , and qacJ , were detected in 24.05%, 21.33%, 30.22%, 8.49%, 18.08%, 10.12%, 10.48%, 12.29%, and 4.15% of isolates, respectively. Notably, the sepA, qacA/B, qacC , and qacJ genes were associated with higher MIC ₉₀ values with CHDG. Additionally, the presence of nor A , mdeA , mepA , sepA , qacA/B , qacC , qacD , qacG , and qacJ genes was associated with increased MIC ₉₀ levels for BZC compared to isolates devoid of these genes (P < 0.05). Conclusion. According to the study, S. aureus has elevated MICs for popular antimicrobial biocides. The most effective compounds are TCS and CHDG, and their presence in personal care products can help control these organisms.