Antibacterial Mechanism of Vanillic Acid on Physiological, Morphological, and Biofilm Properties of Carbapenem-Resistant Enterobacter hormaechei

Abstract

Many studies have evaluated the antimicrobial activity of natural products against various microorganisms, but to our knowledge there have been no studies of the possible use of natural products for their antimicrobial activity against Enterobacter hormaechei. In this study, we investigated vanillic acid (VA) for its antimicrobial activities and its modes of action against carbapenem-resistant E. hormaechei (CREH). The MIC of VA against CREH was determined by the agar diffusion method. The antibacterial action of VA against CREH was elucidated by measuring variations in intracellular ATP concentration, intracellular pH, membrane potential, and cell morphology. Moreover, the efficacy of VA against biofilm formation and VA damage to CREH cells embedded in biofilms were further explored. Our results show that VA was effective against CREH with a MIC of 0.8 mg/mL. VA could rupture the cell membrane integrity of CREH, as measured by a decrease of intracellular ATP, pH, and membrane potential, along with distinctive alternations in cell morphology. In addition, VA exerted a remarkable inhibitory effect on the biofilm formation of CREH and also killed CREH cells within biofilms. These findings show that VA has a potent antibacterial and antibiofilm activity against CREH and, hence, has the potential to be used clinically as a novel candidate agent to treat CREH infections and in the food industry as a food preservative and surface disinfectant. HIGHLIGHTS

Antibacterial activity and mechanism of sanguinarine againstProvidencia rettgeriin vitro

“…CLSM images of P. rettgeri cells within biofilms exposed to 4 MIC of SAG displayed dark red florescence, proving that most of the membranes of cells within the biofilm were damaged. Our study were divided into two main parts, one part demonstrated SAG had antimicrobial activity against P. rettgeri through causing cell membrane dysfunction and changes in cellular morphology, similarlgy a study by Qian et al (2020) , and the other part was the effect of SAG on P. rettgeri biofilm, which showed that different concentrations of SAG could inhibit the formation of P. rettgeri biofilm by changing the biofilm matrix while also killing through mature biofilms in chronic infections. The results were in line with previous reports that showed that SAG inhibits biofilm formation of Candida albicans and Staphylococcus aureus and synchronously reducing extracellular proteins, polysaccharides, and eDNA levels in a dose-dependent manner ( Qian et al, 2020 ).…”

Correlation between Antibacterial Activity and Free-Radical Scavenging: In-Vitro Evaluation of Polar/Non-Polar Extracts from 25 Plants

“…Three of the eight active plant extracts (Salvia palaestina, Micromeria fruticose, and Salvia hierosolymitana boiss) show relatively high free radical scavenging, and four others (Foeniculum vulgare, Cichorium pumilum jacq, Ruta chalepensis, and Chrysanthemum coronarium) show medium free radical scavenging, while the remaining extract (Trigonella foenum-graecum) shows relatively low free radical scavenging. The results show that differences in antibacterial activity among the non-polar extracts cannot always be attributed to antioxidant levels but could be associated with inhibitory effects via other mechanisms of action [39] (inhibition or regulation of enzymes involved in cell wall biosynthesis, nucleic acid metabolism and repair, protein synthesis, or disruption of the membrane structure).…”

Health Promoting Properties of Cereal Vinegars

“…Gallic acid, catechin, and vanillic acid are the major phenolic compounds found in cereal vinegars [17]. The antimicrobial potential of these compounds against various pathogens, such as E. coli, Staphylococcus aureus, Pseudomonas aeruginosa, Enterobacter spp., Listeria spp., Mannheimia haemolytica, Pasteurella multocida, etc., has been demonstrated in several studies [74][75][76][77][78][79].…”