GSE
Body's Beneficial Flora - Health Benefits in GI tract
Benefits of
flora in GI tract
Indigenous bacteria in the human GI tract
perform several beneficial functions for their host. Animal studies have compared germ-free animals (lacking bacterial flora) to those
with flora to demonstrate these benefits, the most important of which include:
1. Normal flora synthesize and excrete vitamins in
excess of their own needs - which can be absorbed by the host.
For example:
• Enteric
bacteria secrete Vitamin K and
Vitamin B12
• Lactic
acid bacteria produce certain B-vitamins .
2. Normal flora prevent colonization by
pathogenic bacteria by competing for
attachment sites or essential nutrients.
Seen in
the oral cavity, intestines, skin, and vaginal epithelium.Experiments have
shown that a handful of Salmonella bacteria can infect
germ-free animals, compared to a million
cells to infect an animal with normal flora.
3. Normal flora may
antagonize other intestinal bacteriathrough the production of substances which inhibit
or kill non-indigenous species. Such substances include nonspecific fatty acids, peroxides,and highly specific bacteriocins (toxins that inhibit growth of closely
related bacterial strains).
4. Normal flora stimulates
the production of cross-reactive antibodies.
Normal flora act as antigens in an animal inducing an antibody-mediated immune
(AMI) response.Low levels of antibodies produced against components of
the normal flora are known to cross react with certain related pathogens, and
thereby prevent infection or
invasion .Antibodies produced against antigenic components of the normal flora are called
"natural" antibodies, and are lacking in germ-free animals.
5. Normal flora stimulates
the development of certain tissues . i.e., the caecum and certain lymphatic tissues (Peyer's patches) in the GI
tract. (the caecum of germ-free animals is larger, thinner-walled, and
fluid-filled compared to conventional animals) Also, intestinal lymphatic
tissues of germ-free animals are less able to be immunologically stimulated.
Reference: Kenneth Todar, PhD.
Online Textbook
of BacteriologyIn the GI Tract . (page 4)
The intestinal microflora provide
protection against a broad range of pathogens
including certain pathogenic forms of:
-
Clostridia.
Main 4 species responsible for disease are:
•
C. botulinum - produces toxin in food/wound
causing botulism; honey can contains spores of C. botulinum , which may
cause infant botulism in humans one year old and younger, but Clostridia
do not compete well with the other rapidly growing bacteria present in the adult
GI tract;
•
C. difficile
- can overgrow other gut bacteria
during antibiotic therapy causing
pseudomembranous colitis;
•
C. perfringens - causes food poisoning, gas gangrene, enterotoxemia ("overeating
disease") in sheep and goats, and more;
•
C. tetani - causative organism of tetanus;
-
Escherichia coli
-
only pathogenic serotypes of E. coli
(variations evolved through the natural
biological process of mutation and horizontal gene transfer from normal,
beneficial gut
E. Coli of the
Enterobacteriaceae
-
Salmonella ,
Shigella
and
Pseudomonas
- Yeasts such as
Candida albicans
Reference
Kenneth Todar, PhD.
Online Textbook
of Bacteriology In the GI Tract
