This document discusses intestinal beneficial bacteria and their health effects. It covers: - The microbiology of the human GI tract and the roles of beneficial bacteria species. - Characteristics of beneficial bacteria like Lactobacillus and Bifidobacterium and how they can provide health benefits. - Conditions that claimed health effects include lactose digestion, cholesterol reduction, reducing colon cancer risk, and improving intestinal and immune health. - Considerations for research on probiotics like bacterial strain selection and dosage. Current issues include unsubstantiated health claims and questions about pathogenic potential in some cases. The concepts of prebiotics and synbiotics that support beneficial bacteria are also introduced.

1. Intestinal Beneficial Bacteria

2. Introduction
• health benefits of fermented foods
• Differences between early beliefs and the current interest
• benefit from consuming vs the scientific basis
 understanding the microbiology and biochemistry of fermented
foods
 microbial ecology of the human gastrointestinal (GI) tract
 roles of some bacteria in the GI tract and in fermented foods in
human health.

3. Introduction
• Researchers are divided in their opinions.
• Some advocate different health benefits that
consumers can have from consuming
fermented foods
• Others doubt those attributes, especially
when "cure-all" claims are made

4. Introduction
• health benefits of foods
• increased interest in foods that are not harshly
processed and preserved
• natural, and fermented foods are considered
natural and healthy
• demand for fermented foods

5. Probiotics
• a product containing living microorganisms,
which on ingestions in certain numbers exert
health benefits beyond inherent general
nutrition
• controversies on the health benefits of
probiotics

6. MICROBIOLOGY OF THE HUMAN GI
TRACT
• GI tract of humans contains more than 1014
microorganisms
• many more than the total number of our body
cells
• metabolically diverse and active
• GI tract harbors ca. 1000 bacterial species
but
• only 30 to 40 species constitute 95% of the
population

7. MICROBIOLOGY OF THE HUMAN GI
TRACT
• The microbial level in the small intestine is ca.
106-7/g
• large intestine = ca. 109-10/g of the content
• small intestine = Lactobacillus and Enterococcus
• large intestine = Enterobacteriaceae, different
species of Bacteroides, Fusobacterium,
Clostridium, Eubacterium, Enterococcus,
Bifidobacterium, and Lactobacillus

8. Infant gut Microflora
• The intestine of a fetus in the uterus is sterile.
• At birth, it is inoculated with flora from the
mother + from the environment.
• From these, the normal flora of the GI tract
are established
• By the second year of life, the population
resembles that of adult GI tracts

9. Intestinal Microflora
• divided into indigenous (autochthonous) and
transient (allochthonous) types
• Indigenous types are permanent inhabitants
(Lactobacillus in the jejunum and ilium, and
Bifidobacterium in the large intestine)
• Transient types are
either passing through
temporarily colonizing a site

10. Intestinal Microflora
• the species and their levels are greatly
influenced by
age
food habits
health conditions
• Initially indigenous types = Lab. acidophilus,
Lab. reuteri, and some Bifidobacterium
• Now = Lab. casei and Lab. Rhamnosus too

11. CHARACTERISTICS OF BENEFICIAL
BACTERIA
• relevant characteristics of Lab. acidophilus, Lab.
reuteri, and Bifidobacterium species
• Gram-positive rods
• grow under anaerobic conditions
• Lab. acidophilus is an obligatory homolactic
fermentator
• Lab. reuteri is a heterolactic fermentator and
produces lactic acid, ethanol, and CO2

12. CHARACTERISTICS OF BENEFICIAL
BACTERIA
• Bifidobacterium species produce lactic and acetic
acids (in 2:3 ratio).
• They are less sensitive to stomach acid
• highly resistant to bile, lysozyme, and pancreatic
enzymes present in the GI tract
• ability to adhere to the intestinal epithelial cells
by Lab. acidophilus strains can be species specific

13. CHARACTERISTICS OF BENEFICIAL
BACTERIA
• help in maintaining the ecological balance of GI
tract microflora
by controlling growth rate of undesirable microflora
ability to metabolize relatively large amounts of lactic and
acetic acids
• can produce specific inhibitory substances(e.g.
reuterine)
• produce bacteriocins
• have an antibacterial effect on both Gram+ and
Gram- bacteria

14. CHARACTERISTICS OF BENEFICIAL
BACTERIA
• able to deconjugate bile acids (to produce compounds that are
more inhibitory than the normal bile acid)
• Produce H2O2
• beneficial effects = when they are present in relatively
high numbers in the intestinal tract (106-7/g intestinal
content)
• Diets rich in foods from plant sources seem to favor
their presence in higher numbers

15. Conditions that reduce bacterial
number
 Antibiotic intake
 Mental stress
 Starvation
 Improper dietary habits
 Alcohol abuse
 Sickness
 Surgery of the GI tract
• Allow the undesirable indigenous or transient bacteria
to grow to high levels and produce enteric
disturbances, including
 diarrhea
 flatulence
 infection by enteric pathogens.

16. Sources of Live cells
• as fermented milk products
such as yogurt (live cells of Lab. delbrueckii ssp.
bulgaricus and Str. thermophilus and is
supplemented with Lab. acidophilus and others)
pasteurized milk (Lab. Acidophilus)
• as supplementation of foods and drinks
• as pharmaceutical products of live cells (in the
form of tablets, capsules, and granules)

17. Beneficial effects from consuming
these live cells
• Ability to provide protection against enteric
pathogens
• supply enzymes to help metabolize some food
nutrients (such as lactase to hydrolyze lactose)
• detoxify some harmful food components and
metabolites in the intestine
• stimulate intestinal immune systems
• improve intestinal peristaltic activity.

18. BENEFICIAL EFFECTS OF PROBIOTICS
• Lactose Hydrolysis
• Reducing Serum Cholesterol Level
• Reducing Colon Cancer
• Reducing Intestinal Disorders
• Modulating Immune Response
• Reducing Allergic Diseases
• Miscellaneous Benefits

19. Lactose Hydrolysis
• Lactose-intolerant individuals
• unable to produce lactase (b-galactosidase)
• produce acids and gas, resulting in fluid accumulation,
diarrhea, and flatulence
• Consumption of yogurt, acidophilus milk, live cells of
Lactobacillus, especially Lab. acidophilus in fresh milk
and pharmaceutical products, reduces the symptoms
• beneficial bacteria supply the needed lactase in the
small intestine

20. Reducing Serum Cholesterol Level
• high numbers of live cells of beneficial intestinal
bacteria = low levels of serum cholesterol in
humans
• The ability of some intestinal lactobacilli to
metabolize dietary cholesterol, thereby reducing
amounts absorbed in blood.
• 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.

21. Reducing Colon Cancer
• undesirable bacteria in the colon have enzymes
that can activate procarcinogens = active
carcinogens = colon cancer
• ability to control growth of undesirable bacteria
in the colon, can reduce the production of these
enzymes.
• By increasing intestinal peristaltic activity, aid in
regular removal of fecal materials = lowers the
concentrations of the enzymes and carcinogens in
the colon

22. Reducing Colon Cancer
• Oral consumption = reduces fecal
concentrations of enzymes of undesirable
colon bacteria such as
b-glucuronidase,
azoreductase, and
Nitroreductase
• contributions of these bacteria in controlling
colon cancer are not clearly known.

23. Reducing Intestinal Disorders
• The undesirable bacteria in the intestine and some
transient pathogens (such as enteric pathogenic
bacteria and Rotoviruses) from the environment can
cause enteric disorders, including infection
• Ingestion of large numbers of live cells of beneficial
intestinal bacteria over a period of time = 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.

24. Reducing Intestinal Disorders
• antibacterial compounds (acids, bacteriocins,
reuterine, and others unknown) = control the
pathogens
• Deconjugation of biles
• increase the specific immunoglobulins
• reduce intestinal permeability
• normalize intestinal microflora

25. Modulating Immune Response
• act on intestinal defense barriers and help regulate
systemic and local immune response
• more effective at an early age, during the development
of lymphoid tissues in the gut microflora
• This beneficial effect is produced possibly by
 changing intestinal permeability
 altering gut microbiology
 improving intestinal immunological barrier functions
 alleviating intestinal inflammatory response

26. Reducing Allergic Diseases
• The normal flora of the GI tract enter the body
through food, water, air, and other environmental
sources
• Raising infants in an oversanitary environment =
interfere with the establishment of normal
microflora
• Probiotics = have a suppressive effect to
inflammatory reaction by stimulating the
production of anti-inflammatory cytokines and
reducing allergic reaction in sensitive individuals

27. Miscellaneous Benefits
• Prophylaxis against urinogenital infection
• Increased calcium absorption from the intestine
• Stimulation of endocrine systems
• Growth promotion
• Prolongation of youth and life

28. SOME ASPECTS TO CONSIDER
• The health benefit theory of fermented foods and
beneficial intestinal bacteria = controversial
• differences in study methods
• In designing these studies, several aspects have
to be recognized
• differences in human responses + differences in
bacterial responses.

29. In selecting bacterial strains, the following
considerations are important:
1. Strain Variation
2. Sensitivity to Stomach Acids
3. Viability and Injury of Cells
4. Dose Level and Duration
5. Induced Lactase Trait
6. Antibacterial Substances
7. True Species and Strains
8. Expertise in Research Areas

30. Strain Variation
• Beneficial strains differ in adherence ability and
specificity
• An adherent strain VS non-adherent strain
• strains adherent to humans VS strains adherent to
other species.
• The selected strains should have a strong adherence
property.
• The adherent property can be lost during long
maintenance under laboratory conditions

31. Sensitivity to Stomach Acids
• Survivability of strains to low stomach pH
varies greatly
• This effect can be reduced
by reducing stomach acidity with food
by using strains that are proven resistant to acid
environment

32. Viability and Injury of Cells
• Cells of beneficial bacteria when frozen, dried,
exposed to low pH, high salts, and many
chemicals can die.
• Among the survivors, many can be injured and
killed by stomach acid and bile salts and lysozyme
in the intestine.
• In studies, it may be better to use cells grown for
16 to 18 h and maintained before feeding under
conditions that retain their maximum viability.

33. Dose Level and Duration
• Consumption of large numbers of live cells
(109 per day), that are not stressed, over a
period of time (ca. 14 d) is advocated to
obtain benefit.
• Use of preparations that have low levels of
viable cells, many of which could be stressed,
cannot provide expected results

34. Induced Lactase Trait
• In Lab. acidophilus, lactase is an induced
enzyme
• To study the lactase effect, strains should be
grown in lactose-containing media.
• In commercial preparations, a strain may be
grown in glucose and thus not have lactase
when consumed.

35. Antibacterial Substances
• Strains of beneficial intestinal bacteria
produce metabolites that are active against
many Gram+ and Gram- bacteria.
• Some of these were identified, such as several
bacteriocins, organic acid, and reuterine.
• Other substances need to be identified and
examined in purified form for their
antibacterial effectiveness.

36. True Species and Strains
• strains used by many probiotic food producers
do not have either proper identity or
information of original sources
• many are not of intestinal origin.
• testing by recommended methods
• the strain being used is what it is supposed to
be.

37. Expertise in Research Areas
• areas of microbiology, gastroenterology,
immunology, oncology etc
• faulty experimental design
• interpretation of data
• differences in response by humans and
animals in feeding trials

38. CURRENT DEVELOPMENTS
• a long list of health benefits are claimed by
manufacturers
• most have not been authenticated by well-
designed scientific studies
• doubts about the beneficial effect of these
products remain

39. A- Standard of Identity
• standard of identity has been established for the beneficial
probiotic bacteria (specially for genus Lactobacillus)
• This includes the ability to
1. adhere to GI epithelial cells
2. interfere with adherence of enteric pathogens to GI
epithelial cells
3. persist and multiply in the GI tract without disturbing the
normal microbial balance
a) produce antibacterial metabolites
b) coaggregate
c) form a normal flora of the GI tract
d) be safe to the hosts.

40. A- Standard of Identity
• 5 strains of lactobacilli are considered
effective for use as probiotics:
(1) Lab. acidophilus NCFM
(2) Lab. casei shirota
(3) Lab. casei CRL431
(4) Lab. rhamonosus GG
(5) Lab. reuteri MM53

41. B- Scientific Status Summary
• A scientific status summary has recently been
published
• listing the diverse species currently being used
by probiotic product manufacturers and their
claims for the bacterial species they are using
• Their claims are not supported by valid
scientific studies and have created disbelief
among consumers

42. To overcome the current controversy
Future research should be directed toward
1. Identifying the phylogeny of a strain
2. Conducting health benefit studies with humans
3. Explaining the exact mechanisms by which a strain produces a
benefit
4. Finding the dose level of viable cells and duration required for a
benefit
5. Determining the ability of a strain to adhere to GI epithelial cells
6. Studying the influence of a probiotic strain on normal GI tract
microflora
7. Determining the proper and effective delivery systems of a
probiotic strain.

43. C- Pathogenic Nature
• Few reports on the isolation of lactic acid
bacteria, from infections in humans
• Lactic acid bacteria = GRAS (generally
regarded as safe) status internationally
• Involvement of these bacteria in health
hazards raised questions about their safety.

44. Answer
• German scientist Paracelsus:
“All substances are poison — the right dose
differentiates a poison and a remedy.”
• From ancient civilization on, people have been
consuming live cells of many of these bacteria
through foods……?

45. Reasons for the infections
1. True identity of a strain is not known + The
products have been produced under
unsanitary conditions
2. Individual may consume a product in large
volume (immuno-compromised)
3. Many isolates from infections have not been
identified correctly to genus and species level
by modern genetic techniques

46. C- Pathogenic Nature
• The incidence of health hazard from beneficial
bacteria, even with all the abuses, is very low
• Use of antibiotics in the treatment of diseases
= the incidence of health risk is much higher.
• True food-grade lactic acid bacteria are safe.

47. D. Probiotics, Prebiotics, and
Synbiotics
• Fuller defined Probiotics as:
“Products containing living microorganisms, which
on ingestion (by humans, animals, and birds) in
certain numbers exert health benefits beyond
inherent general nutrition”.
• The microbial cells should be alive and consumed
in high numbers (usually 109 cells/d)
• Used and consumed for how long (daily as a
preventative or for 2 or more weeks as a curative)

48. Probiotics
• It also does not specify that the mechanisms
by which the health benefits are produced
• In recent studies = specific health benefits can
be achieved by consuming products
containing dead cells or cell components of
beneficial bacteria (e.g., immune modulation)
• It has to be decided in the future whether
they also constitute probiotics

49. Prebiotics
• Beneficial effect = Large no. of probiotic bacteris
1. by consuming a large number of viable cells of
probiotic bacteria
2. by stimulating rapid growth of desirable gut bacteria
by supplying appropriate nutrients
• by supplying one or more selective carbon and
energy sources that are not metabolized by the
bacteria in the small intestine as well as by many
bacteria found in the colon
• gives Bifidobacterium a selective growth
advantage and allows it to reach high numbers

50. Prebiotics
• These nutrients are termed prebiotics and defined as
“Non-digestible food ingredients that beneficially affect
the host by selectively stimulating the growth or activity,
or both, of one or a limited number of bacteria in the
colon, that can improve the host’s health”
Examples
• Lactulose
• Lactitol
• Fructo-oligosaccharides
• Galacto-oligosaccharides
• Lacto-sucrose
• a-inulin

51. Synbiotics
• Probiotics + Prebiotics
• a product containing both, i.e.
“The beneficial gut bacteria in high numbers as
well as nutrient supplement for them will enable
them to multiply rapidly in the gut and produce
health benefit more effectively”

52. E- Biogenics
• The health benefit from the consumption of
fermented dairy products
the lactic acid bacteria used in fermentation
the by-products of metabolism of milk nutrients
by them
• Non-gut bacteria are used in fermentation
(Lactococcus lactis, Str. thermophilus, and Lab.
delbrueckii ssp. Bulgaricus)

53. E- Biogenics
“Biogenics include components in food that are derived
through the microbial metabolic activity of food nutrients
and have health benefits”
Examples:
• Peptide produced by the exoproteinases of some lactic
acid bacteria, such as Lac. lactis in buttermilk
• Lab. delbrueckii ssp. bulgaricus in yogurt
Uses:
• Some of the peptides thus produced and present in the
fermented milk can reduce blood pressure in
individuals with hypertension

54. F- Genome Sequence of Probiotic
Bacteria
• The bacterial species and strains that are
being studied for genome sequence include
several Lactobacillus and Bifidobacterium
species
• Once the complete genome sequences are
obtained, they can be used to compare the
genetic and functional diversities of the GI
tract beneficial bacteria

55. Genetic information can then be used
in the future
• To better understand signaling processes
among gut microbes, intestinal cells, food
components, microbial metabolic products
• To understand mechanisms of beneficial
actions of probiotic bacteria
• Finally, they will help design a better desirable
gut bacteria or specific strains for specific
beneficial effects

56. CONCLUSION
• Fermented foods and some lactic acid bacteria
= help to normalize intestinal microbial
ecosystems
• There are doubts due to differences in results
• These are due to improper uses of bacteria
that have not been tested by well-designed
studies by well-experienced research groups

57. CONCLUSION
• Currently, standards of identity of beneficial
intestinal bacteria are being advocated to
change the myths to reality
• In the future, genome sequence information
will help better understand the interactions of
food, intestinal systems, and microbial species
and strains
• Use them effectively