Nutritional and Therapeutic aspects
Earlier research on indigenous microflora in animals and humans has shown their host-specificity and location-specificity, complexity in composition and their beneficial effects on the hosts. The important effects of probiotics as described in recent literature are summarized below:
SOME OF THE APPLICATIONS OF PROBIOTICS IN ANIMALS AND HUMANS
Individuals with deficiency of the enzyme b-galactosidase (lactase) suffer from abdominal distress when they consume milk or dairy products. These individuals can, however, tolerate yogurt, as more than 50% of the lactose in yogurt is converted into lactic acid by the starter cultures during fermentation. The enzyme can also be released from the organism in the gastrointestinal tract of the consumer and bacterial lactase would be present in the intestine after consumption of the yogurt.
Alm monitored the increase in serum glucose (derived from lactose) in control subjects and in lactose intolerant subjects who were given a 500 ml. dose of milk or yogurt. When given milk, the lactose- intolerant subjects had a much lower rise in serum glucose as compared to the controls. This difference was marginal in the case of yogurt. In a separate study, it was observed that administration of fermented acidophilus milk markedly decreased the breath hydrogen level in lactose-intolerant subjects when compared with the high breath hydrogen levels when taking unfermented milk. Another researcher noted that lactose-intolerant subjects given 18 grams of lactose in yogurt had only about one-third as much hydrogen excretion as in the case of the same amount of lactose in milk or water. There was significant lactase activity in the intestine one hour after ingestion of yogurt. Lactobacillus sporogenes was found to possess considerable b- galactosidase activity when tested in vitro. In vivo studies on the effect of yogurt and fermented milks on lactose digestion have been performed. The results revealed that all samples of yogurt tested dramatically and similarly improved lactose digestion regardless of their b-galactosidase activity. The response to fermented milks varied from marginal improvement with B. bifidus milk to nearly complete lactose digestion with L. bulgaricus milk.
Mechanism of action:
Lactobacilli provide the enzyme b- galactosidase which hydrolyzes lactose. The hydrolyzed lactose is converted to lactic acid as explained in an earlier section describing the metabolism of lactose in lactic acid bacteria.
A variety of studies have examined the proposition that lactobacilli and dairy products fermented with lactobacilli can alleviate gastrointestinal disorders. The results however, are inconsistent, probably due to differences in Lactobacillus strains used as well as variation in conditions of preparation and storage of cultures or fermented products. Results showing significant amelioration of diarrheal symptoms of salmonellosis in weanling rats; salmonellosis and shigellosis in children have been reported. Antibiotic-induced diarrhea was prevented by use of Lactobacillus. The Lactobacillus species used in these studies were L. acidophilus and/or L. bulgaricus. Administration of another strain of Lactobacillus, which produces a broad spectrum bacteriocin, Lactobacillus GG, helped relieve symptoms of relapsing Clostridium difficile colitis resulting from antibiotic treatment for an infection.
Lactobacilli, particularly L. acidophilus and L. Sporogenes* have also been used in the treatment of chronic constipation and flatulence.
Mechanism of action:
Lactobacilli, through the production of lactic acid and bacteriocins create an intestinal environment which is not conducive for the growth of pathogens. Lactic acid also helps relieve constipation by improving the bowel movement.
Immune response system:
Antibodies against intestinal bacteria are commonly detected in healthy humans. These antibodies are produced when the host is stimulated by the antigens of the intestinal bacteria. Defense tissues such as the thymus, lymph nodes, spleen and bone marrow are well developed in conventional mice, but poorly developed in germ free mice, indicating the influence of intestinal flora on the host’s immune response. In more detailed studies with germ-free animals that were fed yogurt, an increase in the levels of immunoglobulins, IgG1, IgG2a , IgG2b and IgM were detected in the serum.
Recent studies have shown that Lactobacillus brevis sub-species coagulans, may enhance the body’s capacity to produce alpha interferon, natural killer (NK) cell activity and 2-5 A-synthase enzyme activity, each important aspect of the body’s natural defenses. Scientists at the Institute Pasteur de Kyoto62 showed that when 10 healthy adults consumed this bacterial supplement, their average producing capacity of alpha interferon increased 65% after two weeks and 59% after four weeks. In the same time frame, natural killer cell activity increased 68% and 47%, as shown in Figure 2.4.
The US Food and Drug Administration has approved alpha interferon for use in treating certain types of cancer, hepatitis and genital warts.
Treatment of vaginitis:
Vaginal infections can be caused by a variety of organisms of which Trichomonas vaginalis. a protozoan parasite, and Candida albicans, a yeast-like fungus are the chief non-bacterial organisms responsible. No single bacterial species is responsible for vaginal infection and hence this type of infection is called non-specific vaginitis (NSV). Symptoms include a gray vaginal discharge, an unpleasant amine smell and "clue" cells, viz., vaginal epithelial cells coated with Gram-variable bacteria. NSV is the most frequent type of vaginal infection. A notable symptom is a significant reduction in the numbers of lactobacilli present and a proliferation of other bacteria in the vaginal environment, including Gardnerella vaginalis and anaerobes.
Lactobacilli are natural inhabitants of the vaginal mucosa. The predominant species is L. acidophilus. Lactobacilli maintain the vaginal pH in the range of 4.0-4.5 through glycogen fermentation to lactic acid. This establishes an environment unfavorable for the growth of pathogens. The level of glycogen in the epithelial cells of the vagina is controlled by circulating estrogens.
Prophylaxis by oral administration of L. acidophilus as well as treatment by intravaginal application of lactobacilli have proved to be effective in the treatment of vaginitis. A commercial formulation using L. sporogenes*, trade marked MYCONIPÒ, is successfully marketed for this indication.
As adjuvant to antibiotic treatment:
The microecological balance of the gut flora is disturbed by treatment with antibiotics. Some of the beneficial flora are killed and on stopping treatment, pathogens begin to re-establish themselves in the intestine. Overgrowth of these organisms and the subsequent invasion of the system by yeast like Candida albicans cause inflammatory, immunologic, neurologic and endocrinologic problems. This occurs due to proliferation and toxin production by these organisms in the host tissues. Administering lactobacilli along with antibiotics helps to prevent this syndrome. The lactobacilli through their metabolic activities establish themselves in the gut, vaginal or oral environment and provide conditions which are non-conducive to the growth of pathogens, Lactobacillus therapy is essential after treatment with anti-amebic drugs.
Drugs such as estrogens and oral contraceptives, if administered during antibiotic treatment, have a significant failure rate. If lactobacilli are administered concurrently, they provide essential intestinal microflora which can correct this situation, by deconjugating drug complexes and keeping the drug in circulation.
Growth-promoting effect of probiotics:
Lactobacilli have been recommended for veterinary use, being effective in restoring the gastrointestinal microecological balance and helping in the establishment of healthy rumen flora. This in turn results in improved health and growth of farm animals.
Mechanism of action:
By reducing the intestinal ammonia concentration and by preventing intestinal infections caused by putrefactive organisms, lactobacilli, particularly L. sporogenes* are effective growth promoters for chicks and domestic animals. This explains the use of probiotics in animal and poultry feeds. In experimental trials with probiotics, it has been found that the effectiveness of treatment depends upon factors such as type, viability and composition of the implanted lactobacilli; type of dosing; and type and age of the recipient animal.