What is a probiotic?

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The term 'antibiotic' is a common term and known to most of us. It refers to compounds that are produced by microorganisms which inhibit the growth of other germs or microorganisms. Antibiotics came into existence in the 20^th century. Before the advent of antibiotics, antiseptics or compounds substances  were in use for long being applied topically or locally  to prevent the growth of microorganisms; they were however ineffective against systemic infections or infections present and spreading in the body. The first compound with antimicrobial activity was pioneered by Erlich in 1911. He centered his investigations on the discovery of a "magic bullet" to treat the dreadful sexually transmitted disease (STD, Venereal disease) syphilis. The first 'sulfa' drug brought in a new era in medicine, when it was shown that the dye 'protosil' protected mice against systemic streptococcal infections as well as cured such infections in infected patients in 1935. Alexander Fleming realized that the mold 'Penicillium' prevented the multiplication of staphylococci and the first antibiotic penicillin came into existence. Streptomycin, tetracyclines, aminoglycosides, semisynthetic penicillins, cephalosporins, quinolones, and other antimicrobials were soon discovered to have similar effects. Recently newer antibiotics have recently been discovered and these include glycylcyclines (tigecycline), lipopeptides (daptomycin), streptogramins (quinupristin-dalfopristin), ketolides (e.g., telithromycin), and oxazolidinones (linezolid).

While a number of countries have contributed to the research and development of antibiotics, Japan is one country that can boast of discoveries of more than 100 useful antibiotics and related medications. The first antibiotic from Japan was colistin (1950) which was followed by: mitomycin C (1955), kanamycin (1957) and bleomycin (1965). Others followed soon - cefazolin (1969), amikacin (1972), piperacillin (1976), norfloxacin (1977), cefoperazone (1978), ofloxacin (1980), clarithromycin (1984), and meropenem (1987). Lately even drugs like   tacrolimus for atopic diseases and pravastatin for hyperlipidemia have been researched and discovered in Japan. Other countries should take note of this and must make more efforts in this direction.

Alas, with all these developments taking place, germs and microorganisms are also at work trying to outdo these drugs by developing resistance. Antibiotics will therefore not always be our magic wand to beat them. We will have to develop and evolve other ways to do it. 

So what is a probiotic?

 First coined in 1965 by Lilley and Stillwell, the term 'probiotic' is derived from the Greek language and means ' for life’. They intended to use this term to describe substances secreted by one microorganism that stimulate the growth of other as opposed to antibiotics that inhibit the growth of other microorganisms. The interpretations kept changing over time and presently the world health organisation (WHO) defines probiotics as  ' live microorganisms which when administered in adequate amounts confer a health benefit to the host'.

 Our ancestors ate probiotics or useful live microorganisms for centuries without actually realizing it in the form of fermented foods such as yogurt, kefir and sauerkraut which contain microorganisms like lactobacilli and bifidobacteria.  Beer, wine, tempeh and cheese are all products of microbial cultures. Lactobacilli and bifidobacteria are two main microorganisms that play a significant role in human health. Lactobacilli are rod shaped, produce lactic acid as a major end product of carbohydrate fermentation and can be isolated from different environments like human gastrointestinal tract, vagina, and fermented diary foods and vegetables.  However the bifidobacteria which are rod shaped and produce acetic acid as their major fermentative end product, are not found in natural fermentative processes and are native to the human intestines.

How do these bacteria reach our intestine?

It is interesting to note that our intestines while we are in the womb are sterile: there are no bacteria. During birth, the baby gets exposed to microorganism s from the birth canal, the mother's fecal organisms and organisms in the environment.  In the beginning enterococci, streptococci and e coli abound in the intestines but soon the baby’s diet of breast milk favors the growth of bifidobacteria and other anaerobes. Breast milk that is produced by the mammary glands may contain up to 10⁹   bacteria/l including lactobacilli and bifidobacteria. However as the baby grows and the feeds change to solid food the flora also changes and organisms like enterococci, bacteroides, streptococci and clostridia increase in large numbers as happen in the adult gastrointestinal tract.

How do probiotics help us?

While the exact mechanism of action of probiotics is unknown, various theories have been proposed.

It has been suggested that probiotics may compete with pathogenic organisms for nutrients which can be aggressively consumed by them thereby inhibiting the growth of the pathogens. For example probiotics can inhibit cl difficile organisms when present in significant numbers by competing with them and utilizing most of the available mono saccharides on which the cl difficile is dependent.

A lot of pathogenic organisms attach themselves to the intestinal mucosa and then go about causing disease. Some strains of lactobacilli and bifidobacteria can attach themselves to the epithelium and act as watchmen preventing pathogens from attaching to the mucosa. For example e coli can be prevented from adhering to the human intestinal cells by lactobacillus rhamnosus strain GG.

A third mechanism by which probiotics act is through the production and release of antimicrobial compounds called Bacteriocins which can kill or inhibit other organisms. Lactobacilli and bifidobacteria can produce bacteriocins and lactobacilli in addition can produce other biologically active compounds like hydrogen peroxide, diacetyl and short chain fatty acids, the release of which is though to improve the intestinal flora and decrease the number of pathogenic organisms. 

Studies have shown that probiotics can stimulate the human immune response by elevating the number of natural killer cells, bettering the phagocytic activity of macrophages and even increasing the secretion of immunoglobulins - leading to a decrease in the number of pathogenic organisms in the GI tract.

What then are the characteristics of a good probiotic?

Well, for one they should be able withstand the gastric acid and bile salts in the gut. They must get easily attached to the intestinal mucosa and finally colonize the intestinal tract thereby displacing and inhibiting some of the pathogenic organisms.

What are the common probiotic microorganisms in use today?

The Bifidobacterium spp (acidophilus) and lactobacillus spp (bifudum) are the most common ones that are useful. Others include enterococcus spp (fecium), bacillus spp (coagulans), sacchoromyces spp (cerevisiae) and streptoccus spp (thermophilus). The action of probiotics is strain specific and only proven strains will actually act as probiotics. To exert therapeutic effects once ingested the bacterial numbers must be more than 10 ⁶/ ml in case of yogurt.

What are the benefits of probiotics?

By taking probiotics we can promote and improve our health. A large number of advantages have been attributed to probiotics. By modifying the intestinal flora we can improve the intestinal digestion, have better motility and function and enhance the absorption of nutrients. In addition gas induced abdominal distension can be reduced, pathogens that colonize the intestine can be suppressed, synthesis of vitamins like k and B can be improved and finally the immune system itself can be stimulated. Probiotics also release bacteriocins which can kill other pathogenic microorganisms.

Research on probiotics have shown that probiotic therapy  can lead to  better treatment of diseases like  bacterial vaginosis, chronic fatigue syndrome, crohn’s  disease, gastrointestinal and vaginal  candidiasis, h pylori infections, gestational diabetes, cl difficile diarrhea’s, and even some  cancer and chemotherapy problems. Probiotics also lead to reduced colds in children, reduction in loose motions or diarrhea, decrease in abdominal distension, and better control of halitosis and eczema.

What are the common probiotics that we can eat to promote good health?

To exert therapeutic effects once ingested the bacterial numbers must be more than 10 ⁶/ ml. Fermented diary products and sour milks have been in use since ages as promoters of good health. Yogurt forms a good medium to transport the probiotic organisms to the GI tract and leads to their better survival. If the yogurt will contain more than 10 ⁶ viable bacteria per ml then a 100 gm serving will provide adequate probiotic bacteria for therapeutic effects.

Fermented vegetables like Kim chi and sauerkraut are common food items in Southeast Asia and Eastern Europe. L plantarum strains are commonly found in these fermented vegetables and these often can withstand the GIT acidity, adhere to the mucosa and colonize them effectively. Most traditionally prepared fermented vegetable usually contain more than 10⁸ living bacteria perm gm so that ten gm may be the minimum dosage required.

Supplemental forms of probiotics include tablets, capsules and powders and they must be in dosage of more that 10⁹ bacteria per dose to have any therapeutic effects.

 

An original article from Dr Alexander+