INFECTION CONTROL
The main target however is the sulphur (thiol)-containing enzymes. These contain common sulphur-hydrogen bonds which give enzymes their shape and activity. In laboratory tests we and others have found that allicin will neutralise key intracellular bacterial enzymes such as alcohol dehydrogenase.
Alcohol dehydrogenases are key to microbes maintaining their redox potentials within cells, which is important to control the microbes general biochemistry. The cells in humans are less affected because of protective cellular mechanisms.
why is allicin not
in everyone’s medicine cabinet? Although this may not be the case in the UK, in Germany the use of gels and oral preparations is very common
In addition to neutralising key biochemical pathways within cells, allicin can prevent the formation of extracellular virulence factors or toxins such as Staphylococcal extracellular toxins A, B, and C1. These can cause intestinal disease.
Initially, our main interest in allicin was in its activity against MRSA. We reported in 2002 that a purified aqueous extract of garlic, which we now describe as a purified aqueous allicin extract, was active against a wide range of clinical isolates of MRSA.
We additionally found that allicin was effective in killing GISAs, highly antibiotic resistant MRSA. In this initial study we also reported a formulation problem when the allicin extract was made-up. Even in an innocuous cream such as Boots aqueous, the activity in the cream was lower than in the equivalent aqueous extract.
Despite the minor reduction in activity with the creams, our initial work with volunteers showed that allicin (500ppm or 0.0005%) cream was still effective in curing chronic MRSA wounds which had been unresponsive to other antimicrobial treatments.
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The concentrations of allicin used in these creams were still significantly lower than the concentrations of agent (2% mupirocin) in the widely used anti-staphlococcal cream Bactroban.
We first presented this work at the European Congress of Clinical microbiology and Infectious Diseases congress in 2005. Patients in this study reported an improvement in their condition after 2 to 6 weeks treatment. This included reduction in pain, redness, irritation and swelling. Infections were resolved in 3 to 4 months.
Since that study we have reformulated our topical allicin and have now a gel which shows equal activity to allicin in water. We have also recently reported that this reformulated gel is active against Group B Streptococcus. GBS infections in neonates can come from vaginal carriage in mothers and is a serious problem and trials are being planned to treat GBS carriage. Even today herbalists suggest the use of garlic cloves to reduce vaginal GBS carriage.
So why is allicin not in everyone’s medicine cabinet? Although this may not be the case in the UK, in Germany the use of gels and oral preparations is very common.
I think one of the issues is that there is a plethora of garlic based products sold over the counter in the UK but not all of them contain allicin.
Some have undergone heat treatment which can destroy allicin and some of the other active agents. There is also an issue with the shelf life of products which do contain allicin. The shelf life, especially with some of the cruder garlic mixtures is not very long (months).
So why not just crush garlic and use it there and then? There are several problems with this. Raw crushed garlic can contain products which can cause skin reactions, it has a strong smell and the activity of the final product, if not checked by chemical analysis, can be extremely variable as it is related to the quality and age of the garlic source used. Overall such a product is unstable and the active content poorly controlled.
For the future we are continuing to concentrate on the use of allicin mainly, but not exclusively, as a topical antimicrobial. Purified or synthetic allicin can be used for the treatment and prevention of disease (i.e. nose/hands for MRSA). We are also developing ways to improve the activity, use and stability of this agent.
We have developed a novel gel formulation which does not reduce the activity of allicin. We can even neutralise its smell. We have also successfully incorporated purified aqueous allicin into an active antimicrobial hand gel to prevent the transmission of disease.
In collaboration with colleagues in chemistry at QMUL, we have now produced and are testing a synthetic allicin. We have found that this agent is very potent and does not have as pungent an odour. Beyond its use against bacteria and fungi we are also testing allicin against a number of viruses.
The development of additional sources of anti-infectives is very important as we still face the continuing progress of antimicrobial resistance in many pathogens including bacteria, fungi and viruses.
Fortunately, there are still many historic sources of antimicrobials still to be developed.
Jul/Aug 10
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