Fall 2004
By Diane Schivera

Beneficial bacteria, such as Lactobacillus acidophilus and Bifidobacterium bifidum, are called probiotics. Probiotics, according to the Food and Agriculture Organization (FAO) of the United Nations, are live microorganisms administered in adequate amounts which confer a beneficial health effect on the host.

The concept of maintaining or restoring the balance of bowel bacteria by introducing live organisms into the gut was first introduced in 1905 by Élie Metchnikoff. The bacteria favorably alter the balance of intestinal microflora, inhibiting the growth of harmful bacteria, promoting good digestion, boosting immune function and increasing resistance to infection. Animals, including humans, with healthy populations of beneficial intestinal bacteria compete more successfully with disease-causing bacteria. Probiotics promote a balance of intestinal flora that produce such organic compounds as lactic acid, hydrogen peroxide and acetic acid. These increase the acidity of the intestine, which inhibits the reproduction of many harmful bacteria. Probiotic bacteria also produce bacteriocins, natural antibiotics that kill undesirable microorganisms.

Safety in Humans

In humans many chronic diseases of the intestinal tract are linked to microorganisms and their actions. More practitioners are looking for ways to prevent or cure these diseases other than anti-inflammatory and antibiotic drugs.

Probiotics and prebiotics have long been used safely in humans. (Prebiotics are dietary carbohydrates that escape digestion in the upper gastrointestinal tract and thus form the predominant substrates for bacterial growth in the colon. Synbiotics is a combination of pro- and prebiotics.) The International Scientific Association for Probiotics and Prebiotics is studying these organisms, and new, more thorough research is isolating probiotics; prebiotics; and carbohydrates such as oligosaccharides, fructooligosaccharides, galactooligosaccharides, lactulos and others that selectively ferment to produce beneficial microbes. Research will evaluate their survivability in the gut and their mode of action.

Probiotics have effectively helped with a range of human aliments. They re-establish beneficial bacteria after normal bowel flora have been destroyed by antibiotics or inflammatory bowel disease. They may help reduce tooth decay by replacing bacteria that destroy the lactic acid-producing bacteria in the mouth. They may alleviate bladder infections, promote wound healing, reduce middle ear infections, ulcers, kidney stones, hypertension or cancer. They may enhance immune system functioning, eliminate toxins from the gut and help reduce allergy development.

Bacteriotherapy using harmless bacteria to displace pathogenic organisms is an alternative, promising way to combat infections and reduce the use of antibiotics. Research is showing that newborn infants who are inoculated with probiotics are more likely to accept the introduced strain, because existing bacteria are not so entrenched and intent on defending against new microflora.

Probiotics More Advanced in Animal Husbandry

The value of probiotics is better established in animal husbandry than in human medicine, and administering pre- or probiotics to improve general health (more efficient food utilization, faster growth rate, increased milk and egg production) and suppress pathogens is accepted practice with various types of domestic animals. (Tannock, G.W., In: Goldberg, I. (ed.), Functional Foods. Chapman and Hall, New York and London, 1995)

People must choose a probiotic carefully, because no legal definition exists, and the term differs among companies that produce probiotics and among nations. Conversely, probiotics for livestock feed must be tested for premarket approval and safety. Strain types, standards of contamination and geographically specific efficacy are tested.

A Lactobacillus species from pig intestines shows the reason for concern: This bacterium may inhibit coliform pathogens on first isolation, but its efficacy may be reduced over time, because bacteria in the intestines constantly compete with other microbial species for nutrients. A Lactobacillus that produces compounds that inhibit other species has a survival advantage. But bacteria are grown commercially in pure culture, and these bacteria would waste energy if they produced an inhibitor that acted against competitors that weren’t present in the pure culture. As a result, members of the population that do not produce the inhibitor could grow a little faster, and every time the cultures are transferred to new media, the proportion of non-inhibitor-producing cells would increase. The bacterial population would lose its inhibitory activity against the pathogen. (“Manipulation of the intestinal microflora for improved health and growth in pigs,” Presented to the British Society for Animal Science (BSAS) conference in Scarborough, March 1999, by Dr. K. Hillman, Microbiology Section, Animal Biology Division, SAC, Ferguson Building, Craibstone, Aberdeen AB21 9YA, U.K.)

The dosage of probiotics for humans is not considered effective at less than 10 colony forming units (cfu) per day. An unhealthy result from any Lactobacillis or Bidobacterium is extremely rare. (Salminen et al.,1998, “Demonstration of safety of probiotics — a review,” Int. J. Food Microbiol. 44:93-106, 400)

Fastrack, one product for ruminants, contains Lactobacillus acidophilus and Streptococcus faecium, which produce lactic acid; yeast, which supplies B vitamins and digestive enzymes; and two nonviable fermentation products that complement the enzymes and B vitamins in yeast. In calves, Fastrack improved weight gains, reduced scours and other digestive disturbances, and increased “thrift” in general – i.e., milk production and appetite increased in cows; feed intake increased in sheep and goats; overall herd health, including coat and conditioning, were improved.

E. coli O157:H7 is the most important enterohemorrhagic (EHEC) serotype (the type of E. coli bacteria) associated with human disease in the United States, but other serotypes of EHEC strains are emerging as important pathogens throughout the world. Among them are E. coli O26:H11 and O111:NM, which are pathogens for humans and young calves. Treating calves with probiotic E. coli bacteria substantially reduced fecal shedding of E. coli. (“Control of EHEC in Cattle by Probiotic Bacteria,” Cathy Brown, Barry Harmon, Suzana Tkalcic, Michael P. Doyle, Tong Zhao and Ping Zhao, University of Georgia.

Escherichia coli is the leading cause of sickness and death in newborn and weaned pigs, also. Roger B. Harvey, a veterinary medical officer at the Southern Plains Agricultural Research Center in College Station, Texas, mixed a culture of beneficial bacteria called “RPCF” – recombined porcine continuous-flow. The RPCF mixture of beneficial bacteria has reduced illness, death and medication costs from E. coli infections.

Studies with poultry at the University of Maryland and at North Carolina State University using a product called Primalac showed that probiotics colonize the gut with beneficial bacteria and exclude such disease-causing organisms as E. coli, Salmonella and Clostridium at sites on the villi of the small intestine, where detrimental bacteria would otherwise destroy the villi. Probiotics increased disease resistance by increasing mucosal villi heights and by increasing the depth of the crypts between the villi, thus increasing the surface area where nutrients can be absorbed. Increased absorption, in turn, increases the efficiency with which animals use feed and increases their survival. The use of antibiotics is also reduced, because the animals are healthier. Studies at the University of Maryland show that Primalac helps animals resist coccidial infection (Emimeria acervulina), which can otherwise devastate a flock of broiler chicks.

Agricultural Research Scientists at the Poultry Microbiological Research Unit in Athens, Georgia, developed the Mucosal Starter Culture to prevent the growth of Salmonella and Campylobacter in newborn chicks. FDA approval of the product is pending. (“Probiotics Protect Poultry From Pathogens,” January 2004, Agricultural Research)

Scientists from the Institute of Food Research (IFR) in Norwich, United Kingdom, reported in April that specific probiotics can destroy pathogenic bacteria living in the gut of poultry, hence helping remove the threat of bacterial food poisoning from the food chain. Also, The FDA/Center for Veterinary Medicine team screened thousands of commensal (non-pathogenic) bacteria from adult chicken guts to identify strains that might have probiotic qualities and found that Lactobacillus johnsonii cleared the pathogenic bacterium Clostridium perfingens from the guts of chicks. This bacterium can exist in the chicken gut without causing disease to the animal, but it has been known to produce toxins associated with necrotic enteritis, which causes poor weight gain and ulcers in poultry. In humans the symptoms of this condition are intense abdominal cramps and diarrhea, sometimes accompanied by vomiting. The probiotic also reduced colonization of the small intestine of poultry by E. coli but did not clear it completely.

Probiotics and Cheese

Probiotics are important to cheese makers. Thermophilic (heat loving) cultures used for yogurt and mozzarella contain Lactobacilli, but mesophilic (moderate temperature) cheese starters usually don’t. Lactobacillus casei and L. rhamnosus grow at 15 degrees C., so they could be used in mesophilic starters. These Lactobacilli are probiotics, and they accelerate the ripening of cheeses and produce exopolysaccharides that may improve the texture and yield of fermented products, according to work done by the Research Network on Lactic Acid Bacteria.

Good News for Dairy Farmers

Dairy foods can protect probiotic bacteria that might otherwise be destroyed while traversing the human digestive tract. Strong acidity in the stomach and high bile concentrations in the small intestine can injure or kill many probiotics. Although some bacteria are more resistant than others to this stress, consumption of probiotics with food, including milk, yogurt and other dairy products, buffers stomach acid and increases the chance that the bacteria will survive into the intestine.

All livestock producers should consider using probiotics preventively, since this represents organic agriculture’s tenet of sustainability. New products will become available over time. However, be sure to check with MOFGA’s Agricultural Services or with MOFGA Certification Services LLC before using a new product if your animals are certified organic.

About the author: Diane Schivera is MOFGA’s assistant director of technical services. You can contact her at 568-4142 or at [email protected] with your questions about animal husbandry.

Immunity and Gut Flora

Lora Hooper, a mucosal biologist at The University of Texas Southwestern Medical Center at Dallas, suggests that “developing mucosal immune cells are poised for interaction with commensal bacteria, and this is very important in shaping the development of the mucosal immune system.” She anticipates profound changes in the perception of these beneficial microbial interactions and their importance in human health and development in the coming years. (The Scientist, Vol. 18, Issue 14, 30; July 19, 2004, “Crossing the Frontlines in Mucosal Immunity – How natural gut flora shape host immune development,” by A. Nicola Schweitzer.)

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