Poly(hexamethylene guanidine): An Effective Compound in Tackling Persistent Bacterial Subpopulations

Area of Science:

• Microbiology
• Polymer Science
• Infectious Diseases

Background:

• Persistent bacteria (PB) are dormant cells that tolerate antibiotics, causing chronic infections and posing a global health threat.
• Developing novel strategies to eliminate PB is crucial for treating recalcitrant infections.

Purpose of the Study:

• To evaluate the antibacterial efficacy of six cationic polymers against persistent bacteria.
• To establish structure-activity relationships for designing effective anti-persistent materials.

Main Methods:

• Systematic evaluation of six cationic polymers against persistent methicillin-susceptible Staphylococcus aureus (MSSA), methicillin-resistant S. aureus (MRSA), and Escherichia coli (E. coli).
• Determination of minimum inhibitory concentration (MIC) and minimum bactericidal concentration (MBC) using microbroth dilution.
• Cytotoxicity assessment against mouse fibroblast (L929) cells via MTT assay.

Main Results:

• Poly(hexamethylene guanidine) (PHMG) exhibited superior antibacterial activity, with MBC values as low as 2 μg/mL against persistent MSSA.
• Other tested cationic polymers showed less efficacy compared to PHMG.
• Structure-activity relationship analysis revealed correlations between polymer charge density, hydrophobic segments, and antimicrobial efficacy.

Conclusions:

• PHMG is a highly effective agent against persistent bacteria.
• This study presents the first library of cationic polymers for targeting persistent bacteria, offering potential strategies for recalcitrant infections.
• Quantitative structure-activity relationships provide a basis for rational design of novel anti-persistent materials.