Activity and mechanisms of action of selected biocidal agents on Gram-positive and -negative bacteria

Abstract

Aims: This study investigates the antimicrobial activity and mode of action of two natural products, eugenol and thymol, a commonly utilized biostatic agent, triclocarban (TCC), and two surfactants, didecyldimethylammonium chloride (DDDMAC) and C 10 -C 16 alkyldimethyl amine N-oxides (ADMAO). Methods and Results: Methods used included: determination of minimum inhibitory concentrations (MICs), lethal effect studies with suspension tests and the investigation of sub-MIC concentrations on growth of E. coli, Staph. aureus and Ps. aeruginosa using a Bioscreen microbiological analyser. Leakage of intracellular constituents and the effects of potentiating agents were also investigated. Only DDDMAC was bactericidal against all of the organisms tested. Eugenol, thymol and ADMAO showed bacteriostatic and bactericidal activity, but not against Ps. aeruginosa. TCC was only bacteristatic against Staph. aureus, but like the other agents, it did affect the growth of the other organisms in the Bioscreen experiments. All of the antimicrobial agents tested were potentiated by the permeabilizers to some extent and leakage of potassium was seen with all of the agents except TCC. Conclusions: DDDMAC was bactericidal against all organisms tested and all compounds had some bacteriostatic action. Low level static effects on bacterial growth were seen with sub-MIC concentrations. Membrane damage may account for at least part of the mode of action of thymol, eugenol, DDDMAC and ADMAO. Significance and Impact of the Study: The ingredients evaluated demonstrated a range of bactericidal and bacteriostatic properties against the Gram-negative and -positive organisms evaluated and the membrane (leakage of intracellular components) was implicated in the mode of action for most (except TCC). Sub-MIC levels of all ingredients did induce subtle effects on the organisms which impacted bacterial growth, even for those which had no true inhibitory effects.

Antibacterial Effectiveness of Selected Moroccan Essential Oils Against the Highly Virulent Jp2 Clone of Aggregatibacter Actinomycetemcomitans

“…The significant antimicrobial activity of all these tested oils could be attributed to its major components. Indeed, the obtained results showed that Origanum compactum was dominated by phenols (thymol 19.21% et carvacrol 22.29%), which are known responsible of bactericidal activity of essential oils [32,33]. Thymol is also present at high concentration (42.01%) in Thymus vulgaris which would also explain the potent antimicrobial activity of this tested oil, as reported in an anterior study [34].…”

“…This may be probably related to chemical composition relative to each tested oils. Indeed, as we mentioned above, phenols, as major compound of Origanum compactum and Thymus vulgaris (but not found in Cymbopogon martinii), are well known responsible of bactericidal activity of essential oils [32,33].…”

Chemical composition and antimicrobial activity of essential oils from selected herbs cultivated in the South of Brazil against food spoilage and foodborne pathogens

“…This essential oil also presented strong to moderate inhibition (MIC and MBC 2.5mg mL -1 ) of the microorganisms used in the microdilution test, and was the second most active of the essential oils evaluated. Basil essential oil was characterized by the presence of linalool, 1,8-cineole and eugenol, which are active against both Grampositive and Gram-negative bacteria (WALSH et al, 2003;SOKOVIC et al, 2007). RUNYORO et al (2010) reported weak to moderate activity of that essential oil (MIC between 10.7 and 12.5mg mL -1 against S. aureus and between 3.14 and 4.25mg mL -1 against E. coli) for two evaluated basil samples that were poor in linalool and eugenol.…”

Antibacterial Effect of Aqueous Extracts and Bioactive Chemical Compounds of <i>Coffea canephora</i> against Microorganisms Involved in Dental Caries and Periodontal Disease

“…Increased membrane permeability is a major factor in the mechanism of antimicrobial action, where compounds may disrupt membranes and cause a loss of cellular integrity and eventual cell death [29]. Despite this information, the antimicrobial potential of the phenolic acids may be different against several microorganisms due to the number and position of substitutions in the benzene ring of phenolic acids and the saturated side-chain and length [30].…”