Introduction to probiotic bacteria

Ever since Alexander Fleming discovered the antibacterial properties of the fungus Penicillium spp. in 1929 (Fleming, 1929), the world has seen a rapid dominance of antibiotics in the treatment of various diseases. The development of broad spectrum and highly specific antibiotics has led to medical science relying heavily on antibiotics as therapeutic agents against different pathogens. There is however certain drawbacks associated with antibiotic therapies. The eliminating action of antibodies does not discriminate between pathogens and the beneficial intestinal microflora. Consequently, an antibiotic therapy also results in an altered intestinal balance causing a number of unpleasant side effects that can persist long after the cessation of treatment. The fast emergence of multiple antibiotic resistant populations of bacteria such as vancomycin- resistant enterococci and methicillin resistant Staphylococcus aureus in hospital environments is also a growing concern among the medical practitioners. Furthermore, some infections once thought readily treatable with antibiotics are now being recognised as serious health threats. For example, a diarrhoeal disease can result from Clostridium difjicile, an opportunistic pathogen, due to the disruption of the normal intestinal microflora during antibiotic treatment. Although this disease is generally treated successfully with a second antibiotic some infections however recur in spite of the antibiotic therapy (Sanders, 1999). Consequently, people all over the world are recognising that preventing or reducing the risk of a disease is preferable to treating diseases. The World Health Organisation recommends global programs to reduce the use of antibiotics in human medicine and suggests increased efforts to prevent diseases through the development of more effective and safer vaccines (Stanton et. al., 2001). A climate has thus been initiated wherein both doctors and patients are searching for preventive rather than curative approaches to diseases in which the intestinal microflora is not adversely affected. One such approach that has rapidly gained popularity is the concept and recognition of probiotics, a general term for nutritional supplements containing one or more cultures of living organisms (typically bacteria or yeast) that, when introduced to a human have a beneficial impact on the host by improving the endogenous microflora (Markowitz and Bengmark, 2002). As compared to the invasive, costly and chemical properties of antibiotics, probiotics scores by being non-invasive, safe, natural, and mostly free of any unpleasant side effects. In recent decades there has been an increase in the prevalence of diseases linked to changes in environmental factors and linking to gut microbiota, providing a rationale for an increased use of probiotics, which can shape the host's immune response.