Low concentrations of antimicrobial agents and their effects on bacterial virulence: A comprehensive literature review

It is now a well-known fact that antibiotic resistance in bacteria has increased with the widespread and uncontrolled use of antibiotics. However, the increase in antibiotic resistance should not be attributed solely to the use of antibiotics. Other antimicrobial agents used in the control of bacterial infections and even heavy metals are also among the factors causing an increase in antibiotic resistance. It is therefore important to study the effects of these agents on bacterial cells. It is generally believed that the selection of resistance typically occurs at high concentrations of antibiotics. However, accumulating evidence demonstrates that selection can also occur at sub-inhibitory levels, making it essential to better understand their impact. While most studies have focused on antibiotics, fewer have examined the influence of biocides, heavy metals, and bioactive components. In this review, we discuss how low concentrations of these agents not only contribute to the development of resistance but also modulate bacterial virulence by affecting biofilm formation, siderophore production, cell morphology, and gene expression. A comprehensive literature review has been conducted, highlighting both the potential risks of these agents in resistance development and their implications for bacterial virulence in the future.