Thursday, August 11, 2011


A recent news item appearing in many media across the world proclaims the discovery of a natural antibiotic, isolated from bacteria and further claims that it can fight against "infamous' food pathogens like Salmonella, E.coli and Listeria. But is it a new discovery? Of course the scientists from Minnesota University who "discovered" the new antibiotic do not claim that the concept of natural antibiotics, different from the conventional ones, is not new as there are a few such well established antibiotics, coming under the category of "Lantibiotics", produced by gram positive bacteria belonging to Streptococcus and Streptomyces groups, effective against other gram positive bacteria with pathogenic potential.

Lantibiotic group of anti microbials are different from conventional antibiotics in that they are polycyclic thioether amino acids containing unusual amino acids like Lanthionine, Methyl Lanthionine, Dehydroalanine and 2-Aminoisobutyric acid. They are chemically dipeptides containing these amino acids. One of the most effective Lantibiotics is Nisin which has been in use for many years, especially by the Dairy Industry and there are others like Epidermin, Duramycin, Mersacidin, Actagardin, Lacticin, Nukacin among 30 such bacterial metabolites already identified by scientists. They are called Lantibiotics to denote that they contain Lanthionine amino acid having antibiotic properties.

How Lantibiotics are different from conventional antibiotics which are several in number, serving humanity ever since Penicillin was discovered by Alexander Fleming in 1948? Unlike normal antibiotics this new class of anti microbial substances do not have the ability to enter the blood stream through the GI tract, limiting their use in internal treatment. They are not stable under the conditions prevalent in the GI tract and are degraded fast losing their activity. Use of Lantibiotics is currently limited to topical applications for fighting skin infections and fast healing of wounds. Coming under the category of Bacteriocins, Lantibiotics work against other gram positive bacterial species either by disrupting cell wall production or interfering with several physiological functions of the host cells, seriously affecting cell multiplication leading to death. Most pathogenic bacteria are fortunately gram positive in nature and there lies the secret of success of Lantibiotics.

A sterling advantage of using Lantibiotics as preservatives for food is their relative safety in terms of development of resistance which is a critical area of concern currently in the meat industry which uses same front line antibiotics made by pharma companies to treat human ailments. According to one estimate more than 80% of antibiotics produced in the US goes to meat industry which uses them liberally to sanitize the meat before marketing. Incorporation of antibiotics in poultry feed is also reported to be in practice, mainly to accelerate the growth of birds and increased meat yield. As meat consumption in the world is growing significantly, human exposure to these antibiotics can lead to development of resistant pathogen strains which will be difficult to treat, calling for newer antibiotics continuously. Many strains of virulent E.coli are known to be unresponsive to treatment with any known antibiotics raising serious questions regarding the advisability of their indiscriminate and uncontrolled use.

The claim by some scientists that Lantibiotics can bring about dramatic changes in the food processing field is somewhat far fetched as of now because of many practical constraints. As these new class of natural preservatives are relatively unstable under a wide range of pH conditions, there is a serious question regarding their reliability under real field conditions. Under basic conditions they are known to undergo oxidation losing their antibacterial property. There appears to be some efforts for evolving analogs of these substances with better stability under different processing conditions and lot needs to be done to identify the type of foods which can be preserved with Lantibiotics. Once the stability issue is resolved, Lantibiotics may become an industry standard. As these are chemically peptide group of compounds, whether there could be allergic complications in some consumers is not known. The safety issues, though not believed to be of any serious nature at present, will gain focus once Lantibiotics become acceptable for wide range use in food products. The technology for producing Lantibiotics in pure condition without artifacts and contaminants, is not considered perfect at present and this is an area requiring further work.

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