-->
The
term 'antibiotic' is a common term and known to most of us. It refers to
compounds that are produced by microorganisms which inhibit the growth of other
germs or microorganisms. Antibiotics came into existence in the 20th
century. Before the advent of antibiotics, antiseptics or compounds
substances were in use for long being
applied topically or locally to prevent
the growth of microorganisms; they were however ineffective against systemic
infections or infections present and spreading in the body. The first compound
with antimicrobial activity was pioneered by Erlich in 1911. He centered his
investigations on the discovery of a "magic bullet" to treat the
dreadful sexually transmitted disease (STD, Venereal disease) syphilis. The
first 'sulfa' drug brought in a new era in medicine, when it was shown that the
dye 'protosil' protected mice against systemic streptococcal infections as well
as cured such infections in infected patients in 1935. Alexander Fleming
realized that the mold 'Penicillium' prevented the multiplication of
staphylococci and the first antibiotic penicillin came into existence.
Streptomycin, tetracyclines, aminoglycosides, semisynthetic penicillins,
cephalosporins, quinolones, and other antimicrobials were soon discovered to
have similar effects. Recently newer antibiotics have recently been discovered
and these include glycylcyclines (tigecycline), lipopeptides (daptomycin),
streptogramins (quinupristin-dalfopristin),
ketolides (e.g., telithromycin), and oxazolidinones (linezolid).
While
a number of countries have contributed to the research and development of
antibiotics, Japan is one country that can boast of discoveries of more than
100 useful antibiotics and related medications. The first antibiotic from Japan was colistin (1950) which
was followed by: mitomycin C (1955), kanamycin (1957) and bleomycin (1965).
Others followed soon - cefazolin (1969), amikacin (1972), piperacillin (1976),
norfloxacin (1977), cefoperazone (1978), ofloxacin (1980), clarithromycin
(1984), and meropenem (1987). Lately even drugs like tacrolimus for atopic diseases and
pravastatin for hyperlipidemia have been researched and discovered in Japan. Other countries should
take note of this and must make more efforts in this direction.
Alas, with all these developments taking place, germs and microorganisms
are also at work trying to outdo these drugs by developing resistance.
Antibiotics will therefore not always be our magic wand to beat them. We will
have to develop and evolve other ways to do it.
So
what is a probiotic?
First coined in 1965 by Lilley and Stillwell,
the term 'probiotic' is derived from the Greek language and means ' for life’. They
intended to use this term to describe substances secreted by one microorganism
that stimulate the growth of other as opposed to antibiotics that inhibit the
growth of other microorganisms. The interpretations kept changing over time and
presently the world health organisation (WHO) defines probiotics as ' live microorganisms which when administered
in adequate amounts confer a health benefit to the host'.
Our ancestors ate probiotics or useful live
microorganisms for centuries without actually realizing it in the form of
fermented foods such as yogurt, kefir and sauerkraut which contain microorganisms
like lactobacilli and bifidobacteria.
Beer, wine, tempeh and cheese are all products of microbial cultures.
Lactobacilli and bifidobacteria are two main microorganisms that play a
significant role in human health. Lactobacilli are rod shaped, produce lactic
acid as a major end product of carbohydrate fermentation and can be isolated
from different environments like human gastrointestinal tract, vagina, and
fermented diary foods and vegetables.
However the bifidobacteria which are rod shaped and produce acetic acid
as their major fermentative end product, are not found in natural fermentative
processes and are native to the human intestines.
How
do these bacteria reach our intestine?
It
is interesting to note that our intestines while we are in the womb are
sterile: there are no bacteria. During birth, the baby gets exposed to
microorganism s from the birth canal, the mother's fecal organisms and
organisms in the environment. In the
beginning enterococci, streptococci and e coli abound in the intestines but
soon the baby’s diet of breast milk favors the growth of bifidobacteria and
other anaerobes. Breast milk that is produced by the mammary glands may contain
up to 109 bacteria/l
including lactobacilli and bifidobacteria. However as the baby grows and the
feeds change to solid food the flora also changes and organisms like
enterococci, bacteroides, streptococci and clostridia increase in large numbers
as happen in the adult gastrointestinal tract.
How
do probiotics help us?
While
the exact mechanism of action of probiotics is unknown, various theories have
been proposed.
It
has been suggested that probiotics may compete with pathogenic organisms for
nutrients which can be aggressively consumed by them thereby inhibiting the
growth of the pathogens. For example probiotics can inhibit cl difficile
organisms when present in significant numbers by competing with them and
utilizing most of the available mono saccharides on which the cl difficile is
dependent.
A
lot of pathogenic organisms attach themselves to the intestinal mucosa and then
go about causing disease. Some strains of lactobacilli and bifidobacteria can
attach themselves to the epithelium and act as watchmen preventing pathogens
from attaching to the mucosa. For example e coli can be prevented from adhering
to the human intestinal cells by lactobacillus rhamnosus strain GG.
A
third mechanism by which probiotics act is through the production and release
of antimicrobial compounds called Bacteriocins which can kill or inhibit other
organisms. Lactobacilli and bifidobacteria can produce bacteriocins and
lactobacilli in addition can produce other biologically active compounds like
hydrogen peroxide, diacetyl and short chain fatty acids, the release of which
is though to improve the intestinal flora and decrease the number of pathogenic
organisms.
Studies
have shown that probiotics can stimulate the human immune response by elevating
the number of natural killer cells, bettering the phagocytic activity of
macrophages and even increasing the secretion of immunoglobulins - leading to a
decrease in the number of pathogenic organisms in the GI tract.
What
then are the characteristics of a good probiotic?
Well,
for one they should be able withstand the gastric acid and bile salts in the
gut. They must get easily attached to the intestinal mucosa and finally
colonize the intestinal tract thereby displacing and inhibiting some of the
pathogenic organisms.
What
are the common probiotic microorganisms in use today?
The
Bifidobacterium spp (acidophilus) and lactobacillus spp (bifudum) are the most
common ones that are useful. Others include enterococcus spp (fecium), bacillus
spp (coagulans), sacchoromyces spp (cerevisiae) and streptoccus spp
(thermophilus). The action of probiotics is strain specific and only proven
strains will actually act as probiotics. To exert therapeutic effects once
ingested the bacterial numbers must be more than 10 6/ ml in case of
yogurt.
What
are the benefits of probiotics?
By
taking probiotics we can promote and improve our health. A large number of
advantages have been attributed to probiotics. By modifying the intestinal
flora we can improve the intestinal digestion, have better motility and function
and enhance the absorption of nutrients. In addition gas induced abdominal
distension can be reduced, pathogens that colonize the intestine can be
suppressed, synthesis of vitamins like k and B can be improved and finally the
immune system itself can be stimulated. Probiotics also release bacteriocins
which can kill other pathogenic microorganisms.
Research
on probiotics have shown that probiotic therapy
can lead to better treatment of
diseases like bacterial vaginosis,
chronic fatigue syndrome, crohn’s disease,
gastrointestinal and vaginal
candidiasis, h pylori infections, gestational diabetes, cl difficile diarrhea’s,
and even some cancer and chemotherapy problems.
Probiotics also lead to reduced colds in children, reduction in loose motions
or diarrhea, decrease in abdominal distension, and better control of halitosis and eczema.
What
are the common probiotics that we can eat to promote good health?
To
exert therapeutic effects once ingested the bacterial numbers must be more than
10 6/ ml. Fermented diary products and sour milks have been in use
since ages as promoters of good health. Yogurt forms a good medium to transport
the probiotic organisms to the GI tract and leads to their better survival. If
the yogurt will contain more than 10 6 viable bacteria per ml then a
100 gm serving will provide adequate probiotic bacteria for therapeutic effects.
Fermented
vegetables like Kim chi and sauerkraut are common food items in Southeast Asia and Eastern Europe. L plantarum strains are
commonly found in these fermented vegetables and these often can withstand the
GIT acidity, adhere to the mucosa and colonize them effectively. Most
traditionally prepared fermented vegetable usually contain more than 108 living
bacteria perm gm so that ten gm may be the minimum dosage required.
Supplemental
forms of probiotics include tablets, capsules and powders and they must be in
dosage of more that 109 bacteria per dose to have any therapeutic
effects.
An original article from Dr Alexander+
