Ethanol antimicrobial effects

There is considerable debate concerning the antimicrobial effectiveness of alcohol used as a skin antiseptic. The antimicrobial efficacy of alcohol is highly dependent upon the concentration used, as well as the moisture level of the microbial environment treated. The short-chain, monovalent alcohols—ethanol and isopropanol—are probably the most effective for skin disinfection, because they are highly miscible with water, have low skin toxicity and allergenic potential, are fast-acting and are microbicidal, as opposed to microbiostatic. 

Other additives to be used in food packaging include ethylene scavengers (e.g., potassium permanganate) on silica, CO2 scavenger (e.g., calcium hydroxide reacting to calcium carbonate), and CO2- generating additives (e.g., ferrous carbonate). Further additives to be used for content protection incorporated in plastics provide antimicrobial effects, for example, silver or ethanol release, antioxidant release, flavor release, flavor absorption, and moisture control [66]. 

The presence of water is essential for the antimicrobial effectiveness of ethanol. Concentrations of 60-70% ethanol in water exhibit the strongest killing action (Price, 1950). Non-sporulating bacteria are rapidly killed by such concentrations, while ethanol at all concentrations does not affect bacterial spores (Russel, 1971). 

As is demonstrated in Table 14 2-phenoxy-ethanol hemiformal is much more effective than 2-phenoxy ethanol itself (see Section 1.7). It may be used alone or in combination with other active ingredients, especially those which exhibit a more fungicidal effect, for the in-can protection of cosmetic products, and also as a preservative for other industrial fluids. Although 2-phenoxy ethanol hemiformal is not mentioned in the EC positive list of preservatives for cosmetic products, there should be no inhibition for this application as it consists of 2-phenoxy ethanol and formaldehyde (addition product) which are registered in the a.m. EC list. Additionally, 2-phenoxy ethanol hemiformal may be regarded as a solvent with antimicrobial effectiveness which proves useful for the formulation of preservatives. 

The most commonly used vehicle is water, for solutions as well as suspensions, emulsions and solubilisates. If a solution is required, co-solvents may be added (see Sect. 5.4.4) such as ethanol, glycerol 85 % and propylene glycol. Then-toxic and adverse effects should be fuUy considered. They are miscible with water and often have an antimicrobial effect as well. Lipophilic active substances may be brought into solution by a lipophilic solvent such as acetem. Another way of processing lipophilic solvents is to convert them into an emulsion. 

Some active substances or excipients have an antimicrobial effect not only through reducing the water activity, but also through a specific antimicrobial mechanism. The best-known example is propylene glycol, but also ethanol, local anaesthetics, chlorpromazine hydrochloride, promethazine hydrochloride and essential oils exhibit a specific antimicrobial effect. In addition, the combination of weak antimicrobial effects of disodium edetate, borax, and boric acid appeared to justify prolongation of the shelf life of non-preserved eye drops over the standard limit of 24 h [48]. 

Kurita, N. and S. Koike, 1983. Synergistic antimicrobial effect of ethanol, sodium chloride, acetic acid and essential oil components. J. Agric. Biol. Chem., 47 67-75. 

The ethanolic extract of P. cupana has antimicrobial effects against Gram-positive and Gram-negative bacteria, as well as antioxidant activity at [tg/mL levels. The antioxidant activity correlates with the levels of phenolic compounds and catechols in the extract. The extract also displayed hepato-and gastroprotective effects when administered to mice and rats at doses below 100mg/kg. ... 

As is apparent from the above information, there is no ideal disinfectant, antiseptic or preservative. All chemical agents have their limitations either in terms of their antimicrobial activity, resistance to organic matter, stability, incompatibility, irritancy, toxicity or corrosivity. To overcome the limitations of an individual agent, formulations consisting of combinations of agents are available. For example, ethanol has been combined with chlorhexidine and iodine to produce more active preparations. The combination of chlorhexidine and cetrimide is also considered to improve activity. QACs and phenols have been combined with glutaraldehyde so that the same effect can be achieved with lower, less irritant concentrations of glutaraldehyde. Some... 

Ayala-Zavala and others (2005) tested the effects of different natural antimicrobial volatiles (methyl jasmonate, ethanol, and their combination) on the phytochemical... 

Olsen, K.M., Gentry-Nielsen, M., Yue, M., Snitily, M.U. and Preheim, L.C. (2006) Effect of ethanol on fluoroquinolone efficacy in a rat model of pneumococcal pneumonia. Antimicrobial Agents and Chemotherapy, 50, 210-219. 

Antimicrobial activity isopropyl alcohol is bactericidal at concentrations greater than 70% v/v it is a mote effective antibacterial preservative than ethanol (95%). The bactericidal effect of aqueous solutions increases steadily as the concentration approaches 100% v/v. Isopropyl alcohol is ineffective against bacterial spores. 

The antimicrobial, anti-inflammatory, wound healing and antioxidant activities of the plant have been documented (26, 29, 30). Various extracts and isolated compounds showed antimicrobial activity. Irobi (31) showed that the ethanolic extract of the plant had bactericidal effect on reference microbial strains and hospital isolates including Bacillus thuringiensis (var Israeli), Bacillus stearothermophilus (NCTC 10339), Staphylococcus aureus (NCTC 6571), Escherichia coli (NCTC 11699), Pseudomonas sp.. Streptococcus faecalis and Klebsiella sp. Isosakuranetin, 4 -hydroxy-5,6,7-... 

Many pharmaceutical emulsifiers are GRAS in food applications. For example, a combination of lactic acid and propylene glycol used on broiler carcasses has been found highly effective in eliminating any salmonel-lae present. The surfactant 12-butyryloxy-9-octadecenoic acid (BOA) is composed of citric acid, EDTA, and sodium lauryl sulfate, and 0.6% of this medium has been found to reduce levels of S. typhimurium cells by >5 log10. Sodium lauryl sulfate resulted in the greatest increase in activity. The addition of ethanol, DMSO, or Span 20 to acids had little or no effect on their antimicrobial activity. In some cases it actually resulted in decreased activity of the acid (Tamblyn and Conner, 1997). 

The weak bacteriostatic effect of ethanolic extracts of Fraxinus ornus bark against Staphylococcus aureus has been reported [31]. The antimicrobial properties of the natural dihydroxycoumarins esculin (1), esculetin (2) and daphnetin have been also investigated using different test systems [32]. However, there was no detailed investigation on the antimicrobial activity of Fraxinus ornus extract and the compounds responsible for have not been identified. 

---