Antibacterial effect of zinc on benzalkonium chloride- tolerant and -sensitive smr+ Staphylococcus aureus

Zn2+ is an important biological element with toxic effects. smr+ Staphylococcus aureus resistant to quaternary ammonium compounds (QACs) have emerged due to a widespread consumption of QAC-containing biocides. This study aimed at assessing zinc sensitivity of Staphylococcus aureus in comparison to Benzalkonium chloride- tolerant and sensitive smr+ strains. Clinical and dairy samples of Staphylococcus aureus were isolated using Mannitol salt agar (MSA) medium at 37 ؛C for 48 hours and subjected to both biochemical and morphological characterization. The presence of smr gene was confirmed by PCR, while Macrodilution broth method was applied for MIC determination. A total of 9 smr+ Benzalkonium chloride-tolerant Staphylococcus aureus strains were isolated from both clinical and dairy samples. Effect of zinc was determined for 20 randomly selected Staphylococcus strains, and MIC values were reported for all 20 strains at a zinc concentration of 20ppm. It was concluded that a zinc concentration greater than 20ppm has an antimicrobial effect on Staphylococcus aureus strains, and that zinc can be used as an antimicrobial agent for biocide resistant strains.