The Use of Catalytic Amounts of Selected Cationic Surfactants in the Design of New Synergistic Preservative Solutions

Abstract

Preservation using combinations of antibacterial molecules has several advantages, such as reducing the level of usage and broadening their antimicrobial spectrum. More specifically, the use of quaternary ammonium surfactants (QAS)—which are profusely used in hair care products and some are known as efficient antimicrobial agents—is limited due to some potential cytotoxicity concerns. This study shows that the concentration of some widely used cosmetic preservatives can be decreased when combined with very small quantities of QAS, i.e., Polyquaternium-80 (P-80) and/or Didecyldimethylammonium chloride (DDAC). The antimicrobial activity of their mixtures was first evaluated by determining the minimum inhibitory concentration (MIC) before and after the addition of QAS. Following up on this finding and targeting an ultimate consumer friendly antimicrobial blend, yet with optimal safety, we chose to utilize the food-grade preservative Maltol as the main natural origin antimicrobial agent mixed with minimum concentrations of QAS to improve its moderate antimicrobial properties. The preservatives were tested for MIC values, challenge tests and synergy using the fractional inhibitory concentration index (FICI). The antimicrobial efficacy of Maltol was found to be synergistically improved by introducing catalytic amounts of P-80 and/or DDAC.

A ten-year microbiological study ofPseudomonas aeruginosastrains revealed diffusion of carbapenems and quaternary ammonium compounds resistant populations

“…Furthermore, the strains showing DS to DDAC circulated throughout the tenyear study period since 2011 and were again estimated at 28.0% by random inclusion among all clinical P. aeruginosa strains of our hospital [33] . It was previously described that the DDAC MICs of susceptible strains were between 15 mg/L [34] and 20 mg/L [35] , which is consistent with our results for a major part of our DDAC-susceptible strains (8-32 mg/L). Interestingly, Goodarzi et al [36] showed that out of 92 P. aeruginosa hospital strains isolated between 2019 and 2020 (Hamadan City Hospital, Iran), 32.6% had a DDAC MIC ranging from 64 to 128 mg/L as found in the present study.…”

The Antimicrobial Mode of Action of Maltol and Its Synergistic Efficacy with Selected Cationic Surfactants

“…Despite the wide usage of maltol, a broader investigation of its antimicrobial mode of action is still needed. In the literature, the antimicrobial efficacy of maltol was evaluated in several studies [4,20,21]. According to the most detailed study, which took place in 1984, maltol inhibited only 10 out of 39 organisms at pH 6, and 5 of 39 organisms at pH 8, and was ineffective against fungi at either pH tested [19].…”

“…F. Schved et al found that maltol, at 20 mmol/L (equal to 2522 ppm), resulted in 0.6 log reduction in CFU/mL of E. coli. However, when added in a combination with nisin, which caused only 0.6 log reduction on its own, they yielded 5.5 log reduction in CFU/mL [20]. In their study, they postulated that maltol destabilize the outer membrane of the Gram-negative E. coli by chelating the positively charged Mg 2+ and Ca 2+ ions, and as a result, permeabilized the cell membrane to enhance the efficacy of nisin.…”

“…Maltol is a promising candidate molecule for medical purposes and an important compound in the food industry; moreover, toxicity studies have determined that maltol is non-toxic and generally recognized as safe (GRAS) [7,18]. The antimicrobial activity of maltol, on the other hand, was only briefly investigated in several previous studies [4,19,20], while its efficacy was suggested mostly as insufficient on its own [19,21]. Recently, we discovered that maltol efficacy can be significantly increased by the addition of only small amounts of selected cationic surfactants [20].…”

“…The antimicrobial activity of maltol, on the other hand, was only briefly investigated in several previous studies [4,19,20], while its efficacy was suggested mostly as insufficient on its own [19,21]. Recently, we discovered that maltol efficacy can be significantly increased by the addition of only small amounts of selected cationic surfactants [20]. In this study, we widened the efficacy studies to better understand the mode of action of maltol and its combination with two cationic surfactants, polyquaternium 80 (P-80), and didecyldimethylammonium chloride (DDAC).…”