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ACADEMY OF VETERINARY, VETERINARY FOOD SAFETY PROGRAMME, DEPARTMENT OF ANATOMY AND PHYSIOLOGY, LITHUANIAN UNIVERSITY OF HEALTH SCIENCES, JOLANTA GIRDAUSKAITĖ, Investigations of the antagonistic properties of lactobacillus-derived antifungal agents, MSc thesis, supervisor: Prof. Vaidas Oberauskas, Ph.
1.2.1 Health benefits of lactic acid bacteria - probiotics
Probiotics, as defined by the World Health Organisation in 2001, are live micro-organisms or their components that, when consumed in adequate quantities, are beneficial to human health
health. It is a microbial food supplement whose main purpose is to restore the balance of the natural intestinal microflora and to improve human health (Knašienė, Rimaitis, 2009). Probiotic preparations are made from micro-organisms, either species of the human microbiota or genetically modified variants thereof. The most common are lactobacilli and bifidobacteria. These bacteria are non-pathogenic and non-toxic and are the main symbionts of the gut and vagina. They are added as food supplements to cottage cheese, yoghurts, kefir, or used in the form of lyophilised powders (capsules, microcapsules), tablets and liquid suspensions (Aukštakalnienė, Radžiūnas, 2006).
Probiotics are thought to have many beneficial functions for the human body. They are used for the prevention and treatment of various diseases. They protect against diarrhoea caused by bacteria and viruses by acting as antagonists to infectious agents (http://www.bifoval.lt/press.php.Prieiga accessed 3 November 2012). In addition, probiotics strengthen the immune system by activating the production of antibodies and the immune response at the cellular level, and they inhibit allergic reactions to food by reducing the permeability of the intestine to allergens and by breaking them down. Probiotics improve the digestion and absorption of food, break down lactose and reduce bloating. There is evidence that they break down carcinogenic substances, protecting the body against cancer (Knašienė, Rimaitis, 2009). Probiotics are recommended:
- In case of diarrhoea caused by antibiotics;
- For diarrhoea of infectious origin;
- Contact Clostridium difficile for diarrhoea;
- Available at Helicobacterpylori infection;
- In inflammatory bowel disease;
- Irritable bowel syndrome;
- In the event of radiation therapy-induced diarrhoea;
- Food allergies, atopic dermatitis;
- Lactose intolerance;
- In the case of travellers' diarrhoea (Fedorak, Madsen, 2004).
The first probiotics with lactobacilli and bifidobacteria appeared in the 1930s (Knašienė, Rimaitis, 2009).
Anthony von Leeuwenhoek was the first to become interested in probiotics in 1676. Around 1850, Louis Pasteur identified the first probiotic bacterium - Lactobacillus. In 1899, Dr Henri Tissier discovered Bifidobacteria, he was the first to try to use bacteria to treat intestinal diseases. Only a few strains of lactobacilli, lactococci and bifidobacteria are considered therapeutic and too little is known about the mechanisms of the gut microbiota. Lactic acid bacteria form an essential part of a healthy gastrointestinal microecology and are closely linked to host metabolism. These bacteria ferment various substrates such as lactose, various amines into short-chain saturated fatty and other organic acids and gases. They also synthesise vitamins, enzymes, antioxidants and bacteriocins. Due to these properties, lactic acid bacteria form an important mechanism that metabolises and detoxifies foreign substances that enter the body (Pavilonis et al., 2005).
There are publications on the effectiveness of probiotics Helicobacter pylori for the treatment and prevention of infections. Helicobacter pylori The bacterium causes type B gastritis and peptic ulcers and is a risk factor for stomach cancer. The research in vitro and in animals, lactic acid bacteria have been shown to inhibit Helicobacter pylori growth and the urease activity it needs to survive in the acidic gastric environment. There are also studies that have shown that probiotics in the human body not only inhibit Helicobacter pylori infection, but also reduces the risk of relapse (Pavilonis et al., 2005).
There has been a lot of research on the effectiveness of probiotics in treating various intestinal infections such as diarrhoea. Evidence shows that probiotics are able to inhibit the proliferation and adhesion of intestinal infectious agents.
In animal experiments it has been shown that Lactobacillus rhamnosus GR-1, Lactobacillus fermentum RC-14 and Lactobacillus rhamnosus GG increases the production of secretory IgA against Salmonella, activates phagocytes and reduces colonisation of the liver and other organs (Mėgelaitis, 2005).
There are several mechanisms that prevent harmful bacteria from attaching to the intestinal epithelium. These include the production and secretion of antimicrobial agents such as bacteriocins and organic acids, competition for adhesion sites, sterile barriers and barriers to compete with and eliminate pathogens. The protective function of lactic acid bacteria is determined by their colonisation capacity, and in this case the adhesion mechanism, which is involved in the formation and maintenance of the wall microflora, is of major importance. This function of lactic acid bacteria determines their ability to enter the wall microflora and become part of the ecological barrier that protects the cells of the macro-organism from the attachment of pathogenic microbes to the mucosa. The species with the strongest adhesive properties are: L. salivarius, L. casei and L. plantarum. L. acidophilus, L. fermentum and L. brevis generally have weak or no adhesive properties. In addition, strains with good adhesive properties have significantly higher antagonistic activity. The antagonistic activity of lactic acid rods has long been of interest to researchers, as lactobacilli show good antagonistic activity in vitro (Bengmark, 1998).
Many scientists believe that the inhibitory properties of lactobacilli are primarily due to the lactic acid they produce, and only secondarily to the antibiotic substances. The bacteriocins of lactobacilli, lectins, have been identified and linked to their colonising capacity.
Thus, the beneficial effects of probiotics on the body are manifested in two ways: topically, by normalising the gastrointestinal microflora, and systemically, by improving the health of the whole organism (Ortwin, 2005).
The following beneficial effects of probiotics on the body are identified:
- Probiotics produce bactericide and hydrogen peroxide;
- Probiotics produce antibiotics such as lactalin, acidophilin and nisin;
- Probiotic organisms displace pathogenic micro-organisms by competing for space and nutrients, and boost the immune system ;
- protects the body against intestinal infections (Rolfe, 2000);
- reduces diarrhoea caused by antibiotics;
- helps with constipation;
- some probiotic microorganisms are able to inactivate the carcinogenic betaglucoronidase and nitroreductase (Guarner et al., 2003);
- production of milk, vinegar, propionate and fatty acids, which leads to a decrease in the pH of the intestinal contents;
- stopping the formation of toxic amines and ammonia;
- Improving digestion, absorption of vitamins and minerals;
- has a positive effect on the body's microflora;
- improving lactose digestion and intestinal peristalsis;
- detoxification of catabolic products from the liver and kidneys;
- anticholesterol, anticarcinogenic, antimutagenic and antiallergenic;
- the production of as yet unidentified growth drivers (Ortwin, 2005).