GSE
Gut Flora,your immune system, which bacteria and environmental factors affecting them
Gut flora - they take care of your
immune system, but are you taking care of them?
Two pounds of bacteria in your gut!
The human intestinal tract is home to more than
400 species of bacteria weighing a total of ~2 pounds.
Concentration of bacteria increases dramatically from the stomach
to the small intestine, to the colon. Bacteria comprise 1/3 dry-weight of feces.
Bacterial flora consist of aerobic and
anaerobic
species. In
a healthy anaerobes
outnumber aerobic bacteria by up to 1000 to 1.
- Anaerobic
flora is dominated by Bacteroides spp., bifidobacteria,
propionibacteria
and clostridia
- Among
aerobic
bacterial flora, the Enterobacteria
Escherichia
coli , a facultative
anaerobe (able to adapt to produce energy from glucose with or without oxygen) of the
enterobacteriaceae
family and Enterococci
(another facultative anaerobe)
predominate. Note that most strains of E. Coli benefit the gut by producing vitamin K2 and keeping a check on pathogenic
bacteria. It is only some of its serotypes (variations) that are pathogenic, and
which can cause intestinal diseases E.g. food poisoning, UTIs and neonatal meningitis.
Appropriately balanced gut flora needed for healthy immune
system
Studies are demonstrating the ability of the gut
flora and oral probiotics to influence systemic inflammation, oxidative stress,
glycemic control, tissue lipid content and even moods.
At least 60%
"Do you have a good "Gut feeling?" can be taken literally
Since most SEROTONIN (the "feel-good"chemical) is produced in the gut.
Benefits of beneficial
flora in GI Tract
A healthy
balance of gut flora is generally considered to be 15% "unfriendly"
bacteria vs. 85% "friendly"bacteria.
This ratio prevents the over colonization
of disease causing micro-organisms (E.g. E. coli and Salmonella)
and competes with and prevents the overgrowth of yeast and fungi.
- Many lifestyle
and environmental factors can upset this balance by harming the "friendlies"-
such as:
• Poor diet - excess sugar/fructose, processed
foods/refined grains, herbicides/insecticides/pesticides;
• Chlorinated/Fluoridated drinking and showering
water
• Too much alcohol
• Pollution - industrial/household chemicals
• Climate
• Aging
• Medication- especially antibiotics/anti-bacterial
soaps (which destroy all bacteria - good and bad), contraceptive pill, and
antacids
• Illness
• Stress
• pH
• Infection
• Geographic location
• Race
• Socioeconomic circumstances
- Symptoms
that your "friendly bacteria" are "Losing the Battle",
include:
• Cravings for sugar and refined carb foods - the "unfriendlies"are
insisting you feed them!
• Gas and bloating / Nausea / Headaches
• Constipation or diarrhea
• Nausea
- A large
part of the influence of the "bad" bacteria is on the intestinal lining
(mucosal barrier). The lining is over 300 square meters (about the size of a tennis
court.)
- For optimum
intestinal flora balance, the beneficial
LACTIC ACID bacteria, such as the
gram-positive
Lactobacilli and
Bifidobacteria , should
predominate (Bifidobacteria
account for ~ 90% of the total colonic beneficial microflora). Presenting a barrier to invading organisms,
they break down food carbohydrates to produce acids
•
LACTO acido
bacillus Inhabits both the small and large intestines
•
Bifidobacteria bifidum .
More prevalent in the large intestine, also the dominant species of
the intestinal tract of breast-fed infants.
Which bacteria reside in the gut?
Upper GI Tract
Esophagus - contains only the bacteria swallowed
with saliva and food
Stomach
Contains mainly acid-tolerant
LACTOBACILLI
Stomach of ~50% of U.S. population have been colonized
by the pathogenic bacteria Helicobacter
Pylori. Responsible for gastric ulcers
and also most likely gastric and duodenal cancer
Small Intestine
The upper small intestine.
Contains relatively sparse
GRAM-POSITIVE flora,
consisting mainly of
LACTOBACILLI and
Enterococcus faecalis .This region has about 105 - 107
bacteria per ml of fluid.
The lower small intestine.
Contains 108 bacteria /mlwith additional species including coliforms
and
Bacteroides
Large Intestine (Colon)
Colon contains bacteria similar to fecal bacteria
Bacteriallevels reach 1011 /ml
feces
BACTERIUM
Range of Incidence ( %)
Bacteroides fragilis 100
Bacteroides melaninogenicus 100
Bacteroides oralis 100
Lactobacillus 20-60
Clostridium perfringens 25-35
Clostridium septicum 5-25
Clostridium tetani 1-35
Bifidobacterium bifidum 30-70
Staphylococcus aureus 30-50
Enterococcus faecalis 100
Escherichia coli 100
Salmonella enteritidis 3-7
Salmonella typhi 0.00001
Klebsiella sp. 40-80
Enterobacter sp. 40-80
Proteus mirabilis 5-55
Pseudomonas aeruginosa 3-11
Peptostreptococcus sp. common
Peptococcus sp. moderate
Methanogens (Archaea)
common
Modified from Youmans, et al.: The Biologic and
Clinical Basis of Infectious Disease. W. B. Saunders Co. Philadelphia. 1985.
Reference
Kenneth Todar, PhD.
Online Textbook of
BacteriologyIn the GI Tract
