Download Lb. acidophilus

Dr. Jehan Abdul Sattar
Probiotics
BENEFICIAL EFFECTS OF PROBIOTICS
In the last 40 years, studies have been conducted to determine
specific health benefits from the consumption of live cells of
beneficial bacteria. Live cells have been consumed from three
principal sources: (1) as fermented milk products, such as
yogurt, which contains live cells of Lb. delbrueckii ssp.
bulgaricus and S. thermophilus and is supplemented with Lb.
acidophilus and others, and pasteurized milk, which contains
Lb. acidophilus; (2) as supplementation of foods and drinks with
live cells of one, two, or more types of beneficial intestinal
bacteria, such as Lb. acidophilus, Lb. reuteri, Lb. casei, and
Bifidobacterium species; and (3) as pharmaceutical products of
live cells in the form of tablets, capsules, and granules.
The beneficial effects from consuming these live cells were
attributed to their ability to provide protection against enteric
pathogens, supply enzymes to help metabolize some food
nutrients (such as lactase to hydrolyze lactose) and detoxify
some harmful food components and metabolites in the intestine,
stimulate intestinal immune systems, and improve intestinal
peristaltic activity.
*Lactose Hydrolysis
People who lack the ability to digest lactose adequately are
classified as lactose maldigestors. (In the past, terms such as
‘‘lactose intolerance’’ or ‘‘lactose malabsorption’’have been
used to describe this condition).
Lactose-intolerant individuals, because of a genetic disorder, are
unable to produce lactase (β-galactosidase) in the small
intestine. When they consume milk, lactose molecules are not
hydrolyzed in or absorbed from the small intestine but passed to
the colon. They are then hydrolyzed in the colon by lactase of
different bacteria to glucose and galactose and then further
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metabolized to produce acids and gas, resulting in fluid
accumulation, diarrhea, and flatulence. Consumption of yogurt,
acidophilus milk, live cells of Lactobacillus, especially Lb.
acidophilus in fresh milk and pharmaceutical products, reduces
the symptoms in lactose-intolerant individuals. This benefit is
attributed to the ability of beneficial bacteria to supply the
needed lactase in the small intestine. However, as Lb.
delbrueckii ssp. bulgaricus and S.thermophilus do not survive
stomach acidity well and are not normal intestinal bacteria, the
benefit of consuming normal yogurt due to the reduced amounts
of lactose in yogurt, as compared to milk, and to the supply of
lactase from the dead cells. The presence of viable starter
cultures in yogurt can be beneficial to lactose maldigestors .
This beneficial action results from presence of β-galactosidase
in the bacterial cells. Apparently being inside the bacterial cells
protects the enzyme during passage through the stomach so that
it is present and active when yogurt reaches the small intestine.
In contrast, the intestinal bacteria, especially some Lactobacillus
species, could, under proper conditions, colonize the small
intestine and subsequently supply lactase.
Once the yogurt culture reaches the small intestine,it interacts
with bile, which increases permeability of the cells of these
bacteria and enables the substrate to enter and be hydrolyzed.
The enzyme remains inside the cell upon exposure to bile rather
than leaking out into the surrounding medium. As mentioned
previously, the starter cultures used for yogurt manufacture (Lb.
delbrueckii subsp. bulgaricus and S. thermophilus) are not bile
resistant and thus are not expected to survive and grow in the
intestinal tract. Despite this limitation, consumption of these
bacteria provides a means of transferring β-galactosidase into
the small intestine where it can improve lactose utilization in
lactose maldigestors.
Nonfermented milk containing cells of Lb. acidophilus also can
be beneficial for lactose maldigestors . This organism, unlike
the yogurt starter cultures, can survive and grow in the intestinal
tract. However, a similar mechanism in improving lactose
utilization in lactose maldigestors to that observed for yogurt
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bacteria is probably involved. β-Galactosidase activity of cells
of Lb. acidophilus is greatly increased in the presence of bile
because of increased cellular permeability. As with yogurt
cultures, cells of Lb. acidophilus do not lyse in the presence of
bile, but their permeability is increased permitting lactose to
enter the cells and be hydrolyzed. Because Lb. acidophilus can
survive and grow in the intestinal tract, it is reasonable to
expect, however, that additional β-galactosidase may be formed
after ingestion of milk containing this organism.
The ability of probiotic enzymes to aid digestion has also been
studied in infants with sucrase deficiency. The ability to digest
sucrose was augmented by the ingestion of Saccharomyces
cerevisiae, a yeast that produces the sucrase enzyme.
* Reducing Serum Cholesterol Level
Consumption of fermented dairy product and high numbers of
live cells of beneficial intestinal bacteria has been associated
with low levels of serum cholesterol in humans. This is
attributed to two possible factors. One is the ability of some
intestinal lactobacilli to metabolize dietary cholesterol, thereby
reducing amounts absorbed in blood. The other possibility is
that some lactobacilli can deconjugate bile salts and prevent
their reabsorption in the liver. The liver, in turn, uses more
serum cholesterol to synthesize bile salts and indirectly helps
reduce cholesterol level in serum. There are many of probiotic
organisms that can help to control serum cholesterol levels.
Some of these include Lb. casei , Lb. acidophilus and
Bifidobacterium species .
* Reducing Colon Cancer
Many of the undesirable bacteria in the colon have enzymes that
can activate procarcinogens, either present in food or produced
through metabolism of undesirable bacteria, to active
carcinogens that, in turn, can cause colon cancer. Beneficial
intestinal bacteria, both Lactobacillus and Bifidobacterium
species, by their ability to control growth of undesirable bacteria
in the colon, can reduce the production of these enzymes. Also,
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beneficial bacteria, by increasing 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. Lb. acidophilus, Lb. casei,
and Lb. delbrueckii subsp. bulgaricus are species most often
mentioned as having potential to provide anticarcinogenic
actions. For Lb. delbrueckii subsp. bulgaricus, the
anticarcinogenic action is associated with substances produced
by the organism during manufacture of yogurt as opposed to
being produced in the body following consumption of yogurt.
However, for Lb.acidophilus and Lb. casei growth or action in
the gastrointestinal tract seems to be important. Part of the
benefit may involve direct effects in inhibiting tumor formation.
However, the main effect may result indirectly through
inhibiting growth of undesirable bacteria that form carcinogens
in the large intestine.
* Modulating Immune Response
Enhancement of the body’s immune response by consuming
cells of certain lactobacilli increases resistance of the host to
intestinal infections . Of the lactobacilli, Lb. casei seems to be
the primary one involved . B. longum also can stimulate the
immune system to control E.coli in the gastrointestinal tract.
Researchers in this area have suggested that this action involves
activation of macrophages which in turn destroy pathogenic
organisms in the body. It also has been suggested that
consumption of these organisms is followed by secretion of
components into the intestinal tract which are inhibitory toward
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certain of the foodborne pathogens. This enhancement of the
immune system increases the host defense mechanisms and
could be very important for control of foodborne illnesses. This
may be a key explanation as to how certain probiotic
microorganisms used as dietary adjuncts can exert control over
intestinal infections.
* Reducing Allergic Diseases
Probiotics containing beneficial bacteria can have a suppressive
effect by stimulating the production of anti-inflammatory
cytokines and reducing allergic reaction in sensitive individuals.
Probiotics Lb. rhamnosus GG appears able to reduce atopic
disease, not only in infants receiving the probiotic directly, but
also where the mother was given the bacterium. Some studies
have suggested that an increase in IL-10 in the serum of infant
receiving Lb. rhamnosus GG may be responsible for the
probiotic effect. Further evidence has suggested that probiotics
not only reduce symptoms of atopic disease, but that they can
also prevent such conditions from occurring when given
prenatally to mothers.
* Reducing Bacterial vaginosis and UTI
The vaginal micro flora of healthy human females typically
comprises about 50 bacterial species. This micro biota is mainly
comprised of lactobacilli, which are known to protect the host
from colonization by pathogens.
In health, epithelial cells lining the vagina are covered with a
biofilm in which lactobacilli predominate, and most pathogens
are unable to colonize the biofilm.
However, breakdown of the biofilm is known to occur in BV,
although the ecological and physiological mechanisms involved
are unclear.
Probiotics are increasingly being regarded to be of therapeutic
benefit in BV, partly because of the large numbers of
lactobacilli in the healthy vaginal microflora and also because
their loss is implicated in disease pathogenesis.
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Studies on urogenital tract infections, characterized by
decreases in the protective lactobacilli genera, revealed that
inserted capsules or oral dosages of a probiotic combination,
containing Lb. rhamnosus GR and Lb. fermentum RC-14,
restored the vaginal flora to a healthy composition in 90% of the
women treated. However, several trials using lyophilised Lb.
acidophilus applied locally or Lb. acidophilus yoghurt given
orally has generated similar results. Other studies have
investigated the therapeutic benefits of Lb. rhamnosus GR-1 and
Lactobacillus fermentum RC-14 given orally. In vitro
experiments suggested that these bacteria possessed several
properties, such as adhesion to epithelial cells and production of
antimicrobial substances, that could be of clinical value . Further
work has suggested that a dose of at least 108 cfu / d of Lb.
rhamnosus GR-1 and Lb. fermentum RC-14 is needed for a
therapeutic effect . It is therefore likely that any probiotic
therapy capable of reducing or preventing BV will also have a
beneficial effect on UTI. Indeed, vaginal administration of two
capsules per week containing 109 cfu Lb. rhamnosus and Lb.
fermentum was found to reduce the UTI recurrence rate to that
expected with antibiotic therapy .
Reducing Intestinal Disorders
Under certain conditions, indicated before, 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 Rotoviruses)
from the environment can then cause enteric disorders,
including infection. 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
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antibacterial compounds (acids, bacteriocins, reuterine, and
others unknown), 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.
-Probiotics in Clostridium difficile-associated intestinal
disease
Clostridium difficile is a pathogenic bacterium that takes
advantage of the compromised GI tract in ~20 to 40% of
patients suffering from antibiotic-associated diarrhoea.
Intervention with Saccharomyces boulardii in a placebocontrolled trial has shown that the use of this probiotic as an
adjunct to the antibiotic therapy prevented relapse .
Furthermore, a recent study has shown that probiotic intake
reduced the incidence of C. difficile toxin-positive patients as
compared to the placebo group .Also Lactobacillus GG was
successfully used to treat patients with recurrent diarrhoea
caused by C. difficile .
-Probiotics in Antibiotic-associated diarrhoea
The use of antibiotics to treat infection has devastating
consequences on gastrointestinal balance (and particularly upon
beneficial bacteria) that can result in diarrhoea in up to 20% of
patients receiving antimicrobial therapy. Several well-designed,
placebo-controlled randomized trials have demonstrated that S.
boulardii, Lactobacillus rhamnosus GG and Enterococcus
faecium SF68 were effective at reducing the incidence of
diarrhoea in this patient population.
Evidently, antibiotic therapy disrupts the intestinal microbiota;
however, it is unclear how these probiotics mediate their
protection. It is conceivable that they may prevent the growth of
pathogens such as C. difficile, or fortify the epithelial barrier.
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-Probiotics in Acute diarrhoea and gastroenteritis
Acute diarrhoea can be caused by rotavirus infection, which is
a serious contributor to infant morbidity and mortality,
especially in developing countries. Several studies have been
conducted with reports of decreases in the incidence and
duration of diarrhoea by a decrease in the shedding of rotavirus,
following probiotic ingestion of strains such as Lb.rhamnosus
GG, Bifidobacterium bifidum and Streptococcus thermophilus .
Probiotics need to be viable to exert inhibitory effects. This is
because competitive mechanisms such as acid formation,
antimicrobial excretion, substrate limitation and occupation of
colonization sites all require viability. Also Campylobacter
jejuni ( C. jejuni) is an important cause of bacterial-induced
enterocolitis in humans in the developed world, caused by
consuming infected food.
Multiple studies have shown that Lactobacillus, administered
orally, may have antidiarrhoeal properties. The ability of
lactobacilli to inhibit C. jejuni invasion. Also the effect of the
yeast Saccharomyces boulardii on acute diarrhoea was
described by shortening the duration of diarrhea.
-Probiotics in Constipation and Bloating
Constipation is a common heterogeneous gastrointestinal
disease affecting up to 27% of the western population. Although
there is evidence supporting the fact that probiotics modify the
intestinal function. The effect of a probiotics in 266 females
with functional constipation, randomized to receive either a
mixture of Bifidobacterium animalis and prebiotic
fructooligosaccharide (FOS) twice a day for 2 weeks. The
results show a 22% increase in the number of bowel movements
per week and a slight increase in stool quality when compared to
placebo.
*Other health benefits:
Many other health benefits of probiotics have been claimed,
such as increased calcium absorption from the intestine,
stimulation of endocrine systems, growth promotion,
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prolongation of youth and life, production of vitamins(folate
,vitamin B12,vitamin K2, riboflavin and thiamine) has been
claimed among the causal relationships of the healthy benefits
of probiotics and production of Exopolysaccharide(EPS) have
been reported to exert a number of beneficial health effects,
including prebiotic , immunomodulating , anti-tumoral,antiulcer and cholesterol-lowering effects .
The nasopharyngeal microbiota of children suffering from
recurrent otitis media has also been alleviated through the
application of a nasal spray containing probiotic microorganisms.
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