Intestinal Bacteria and Probiotics ◾ 199
intestinal peristaltic activity, aid in regular removal of fecal materials. This, in turn, lowers the
concentrations of the enzymes and carcinogens in the colon and reduces the incidence of colon
cancer. Several studies have shown that oral consumption of large numbers of live cells of the
beneficial bacteria reduces fecal concentrations of enzymes such as β-glucuronidase, azoreductase,
and nitroreductase of undesirable colon bacteria. However, the relationship between reduction of
these enzymes and reduction in colon cancer from the consumption of beneficial intestinal bacteria has not been studied, and thus contributions of these bacteria in controlling colon cancer are
not clearly known. Animal studies have shown that formation of aberrant cysts, considered to be
putative precancerous lesions, is reduced by consuming live cells of beneficial GI tract bacteria,
especially bifodobacteria. Again, the results are not consistent, which could be a result of the factors listed previously.
Prevention and Control of Enteric Infections
Under certain conditions, as indicated previously, the intestinal population of beneficial bacteria
can be reduced. The undesirable bacteria in the intestine and some transient pathogens (such as
enteric pathogenic bacteria and viruses) from the environment can then cause enteric disorders,
including infection, IBD, and UC. Infection results from the invasion and growth of enteric
pathogens in the intestine. Ingestion of large numbers of live cells of beneficial intestinal bacteria over a period of time was reported to reduce these problems. Both infants and adults on oral
antibiotic therapy can develop diarrhea because of a loss of desirable bacteria in the intestine and
an increase in undesirable pathogenic bacteria and viruses. It was suggested that beneficial bacteria, when consumed in large numbers, establish in the intestine and produce antimicrobial compounds (acids, bacteriocins, reuterine, etc.), which, in turn, control the pathogens. Deconjugation
of biles by beneficial species also produces compounds that are more antibacterial than the bile
salts; this has also been suggested as a mechanism to control the growth of undesirable enteric bacteria. Probiotic bacteria also increase the specific immunoglobulins, reduce intestinal permeability,
and normalize intestinal microflora. In many studies, the results were not always positive. This,
again, could be a result of the variation in study methods, as described previously, including the
use of strains without the specific trait. Probiotics are reported to control enteric viral and bacterial infections, including rotavirus, Norovirus, Campylobacter, Salmonella, Vibrio, Escherichia coli
O157:H7 and antibiotic associated Clostridium difficile. 8
Modulating Immune Response
Limited studies have shown that intestinal microorganisms act on intestinal defense barriers and
help regulate systemic and local immune response. This is more effective at an early age, during
the development of lymphoid tissues in the gut. Normal establishment of GI tract flora at an early
age helps develop immunity to oral administration of antigens associated with an inflammatory
reaction in the gut. Oral administration of probiotic gut flora also helps overcome some immune
responses caused by the undesirable gut microflora. This beneficial effect is possibly produced by
changing intestinal permeability, altering gut microbiology, improving the intestinal immunological barrier functions, and alleviating intestinal inflammatory responses. Probiotic bacterial
cell wall components, especially the peptidoglycan molecules, are thought to be responsible for
immunomodulatory function. Specific immune modulation function of probiotics includes the
activation of cellular and humoral immune responses. Cellular immune response includes activation of T helper cells to produce cytokines that, in turn, activate phagocytic cells for clearance of
intestinal peristaltic activity, aid in regular removal of fecal materials. This, in turn, lowers the
concentrations of the enzymes and carcinogens in the colon and reduces the incidence of colon
cancer. Several studies have shown that oral consumption of large numbers of live cells of the
beneficial bacteria reduces fecal concentrations of enzymes such as β-glucuronidase, azoreductase,
and nitroreductase of undesirable colon bacteria. However, the relationship between reduction of
these enzymes and reduction in colon cancer from the consumption of beneficial intestinal bacteria has not been studied, and thus contributions of these bacteria in controlling colon cancer are
not clearly known. Animal studies have shown that formation of aberrant cysts, considered to be
putative precancerous lesions, is reduced by consuming live cells of beneficial GI tract bacteria,
especially bifodobacteria. Again, the results are not consistent, which could be a result of the factors listed previously.
Prevention and Control of Enteric Infections
Under certain conditions, as indicated previously, the intestinal population of beneficial bacteria
can be reduced. The undesirable bacteria in the intestine and some transient pathogens (such as
enteric pathogenic bacteria and viruses) from the environment can then cause enteric disorders,
including infection, IBD, and UC. Infection results from the invasion and growth of enteric
pathogens in the intestine. Ingestion of large numbers of live cells of beneficial intestinal bacteria over a period of time was reported to reduce these problems. Both infants and adults on oral
antibiotic therapy can develop diarrhea because of a loss of desirable bacteria in the intestine and
an increase in undesirable pathogenic bacteria and viruses. It was suggested that beneficial bacteria, when consumed in large numbers, establish in the intestine and produce antimicrobial compounds (acids, bacteriocins, reuterine, etc.), which, in turn, control the pathogens. Deconjugation
of biles by beneficial species also produces compounds that are more antibacterial than the bile
salts; this has also been suggested as a mechanism to control the growth of undesirable enteric bacteria. Probiotic bacteria also increase the specific immunoglobulins, reduce intestinal permeability,
and normalize intestinal microflora. In many studies, the results were not always positive. This,
again, could be a result of the variation in study methods, as described previously, including the
use of strains without the specific trait. Probiotics are reported to control enteric viral and bacterial infections, including rotavirus, Norovirus, Campylobacter, Salmonella, Vibrio, Escherichia coli
O157:H7 and antibiotic associated Clostridium difficile. 8
Modulating Immune Response
Limited studies have shown that intestinal microorganisms act on intestinal defense barriers and
help regulate systemic and local immune response. This is more effective at an early age, during
the development of lymphoid tissues in the gut. Normal establishment of GI tract flora at an early
age helps develop immunity to oral administration of antigens associated with an inflammatory
reaction in the gut. Oral administration of probiotic gut flora also helps overcome some immune
responses caused by the undesirable gut microflora. This beneficial effect is possibly produced by
changing intestinal permeability, altering gut microbiology, improving the intestinal immunological barrier functions, and alleviating intestinal inflammatory responses. Probiotic bacterial
cell wall components, especially the peptidoglycan molecules, are thought to be responsible for
immunomodulatory function. Specific immune modulation function of probiotics includes the
activation of cellular and humoral immune responses. Cellular immune response includes activation of T helper cells to produce cytokines that, in turn, activate phagocytic cells for clearance of