Antimicrobial Activity of L-Lysine and Poly-L-Lysine with Pulsed Electric Fields

For the first time, the possibility to use L-lysine (Lys) and poly-L-lysine (PLL) as additives with pulsed electric fields (PEF) for antimicrobial treatment is reported. The antimicrobial efficacy of Lys and PLL for Escherichia coli, Staphylococcus aureus, Trichophyton rubrum and Candida albicans was determined. Inactivation of microorganisms was also studied by combining Lys and PLL with PEF of 15 and 30 kV/cm. For PEF treatment, pulses of 0.5, 1, 10 or 100 mu s were applied in a sequence of 10 to 5000 at 1 kHz frequency. The obtained results showed that 100 mu s pulses were the most effective in combination with Lys and PLL for all microorganisms. Equivalent energy PEF bursts with a shorter duration of the pulse were less effective independently on PEF amplitude. Additionally, various treatment susceptibility patterns of microorganisms were determined and reported. In this study, the Gram-negative E. coli was the most treatment-resistant microorganism. Nevertheless, inactivation rates exceeding 2 log viability reduction were achieved for all analyzed yeast, fungi, and bacteria. This methodology could be used for drug-resistant microorganism's new treatment development.

Automated summary

This study reports for the first time the possibility of using L-lysine and poly-L-lysine as additives with pulsed electric fields for antimicrobial treatment. The combination of Lys and PLL with PEF was found to be most effective with 100 μs pulses for all microorganisms. Different treatment susceptibility patterns of microorganisms were observed, with Gram-negative E. coli being the most treatment-resistant. Despite this, inactivation rates exceeding 2 log viability reduction were achieved for all analyzed yeast, fungi, and bacteria, showing potential for new treatment development for drug-resistant microorganisms.