The 20th century was the age of antibiotics and corticoids, the 21st century will be the age of probiotic and immunity .
Probiotic is now worldwide, one of the main interests in the field of medicine. Many people use probiotic, prescribe it and recommend it. Millions of articles are produced as reviews and trials. Studies are done all over the world; symposia and congresses are very active in this field, even societies are formed to revive the probiotic kingdom. Commercially, probiotics have been over used and recommended by many companies. Probiotics became a must in infant feeding especially milk formulas. So what is probiotic and how do we have to approach this phenomenon?
Probiotics are defined as “live micro-organisms which, when administered in adequate amounts, confer a health benefit on the host” . Probiotics are viable microbial dietary supplement. They are living micro-organisms used as food additives having a beneficial effect on the host by improving digestion and intestinal hygiene [3,4].
In order to use viable bacteria, there are some criteria. The bacteria must be safe for consumption such that they are not pathogenic and do not carry antibiotic resistance genes and do not degrade intestinal mucosa or conjugate for bile acids. They should survive intestinal transit (must be acid and bile tolerant), and be able to adhere to mucosal surface and colonize the intestine. They must also produce antimicrobial substances and antagonize pathogenic bacteria and be stable during processing and storage .
There are many misconceptions and myths regarding probiotics. Not all probiotic supplements are the same. They could have different effects on health and cannot replace medications. Not all food and supplement labels provide accurate microbe counts. As for yogurts, they contain probiotics but are not generally a good source of probiotics. The best probiotics are kept in the fridge is not always true and lyophilisation does not ensure that the probiotics remain viable at room temperature. Probiotics should not be used while taking antibiotics is not necessary true .
Another common misconception is that probiotics must always colonize the intestinal tract to exert their effects. Some probiotics such as Bifidobacterium longum and Bacteroides become part of the human intestinal microflora, whereas others such as Lactobacillus casei and B. animalis may not, they may stay and adhere from few days to weeks and then are excreted . Non colonizing probiotics indirectly exert their effects either in a transient manner as they pass through or by remodeling or influencing the existing microbial community .
Are probiotics safe? Do they have side effect on the person using them? Do they have adverse effect on infants and children? These questions come to every mind whenever we are using probiotic for long time. Infection is the first to come to our mind. In the literature there are cases of infection such as endocarditis or bacteremia . Liver abscess caused by lactobacillus rhamnosus was also reported . A review of 200 cases of lactobacillus infection between 1950-2003 revealed 114 cases of bacteremia with mortality rate 32%. All patients had significant morbidity including malignancy, 62 cases had endocardidtis with mortality rate 22.9% .
Several attempts have been made to evaluate the factors that predispose severely ill patients to infection by probiotics, but statistical analysis is lacking and the number of cases is very small to permit the drawing of any firm conclusion associated with endocarditis and bacteremia . Lactobacillus was also associated with other infections including meningitis, peritonitis, and abscesses .
Probiotics given to people with severe underlying disease
may cause systematic infection as bacteremia and fungemia
. Bacteremia was reported in premature babies with shortgut
syndrome . Probiotics have been shown to be safe in
immunocompetent hosts in an outpatient setting. Nevertheless,
administration of probiotics to immunocompromised, chronically
ill, hospitalized patients with GI disorders and indwelling
catheters may predispose to probiotic sepsis since probiotics
may increase translocation of bacteria into the bloodstream
. The use of probiotics during pregnancy, in neonates, and in
children has not been associated with any adverse immunologic
effects . There are other effects than infection. Metabolic
and enzymatic effect: theoretically probiotics may have some
effect on metabolism of bile salts and mucous (not yet reported).
Immunological effects: Immune deficient patient ingesting large
amounts of certain probiotics can lead to relapse of autoimmune
Gene Transfer: Genetically modified probiotics used
may harbor antibiotic resistant genes. The risk would be in
transferring antibiotic resistance genes to the host. For example,
L reuteri and L plantarum have been found to carry such genes
Probiotics might not be effective in pancreatitis .
Probiotics might not be a treatment for asthma. A review stated
that trials of the effect of probiotics on asthma are limited and
show conflicting results . Interestingly, reduced microbial
diversity was associated with diseases such as Crohn’s disease
and eczema in early life [18,19]. Hence, one of the actions of
probiotics might be to restore microbial diversity in dysbiosis.
As with diseases, most probiotics tested to date are more
effective than placebo in inducing or maintaining inflammatory
bowel disease remission. There is good evidence to support the
efficacy of S. boulardii and LABs and the combination of the two
for antibiotic associated diarrhea, VSL#3 for pouchitis, and B.
infantis 35624 for irritable bowel syndrome . Probiotics
reduce the duration of symptoms in acute infectious diarrhea
. Probiotics, including E. coli Nissle 1917, LGG, and VSL#3
are as effective as standard therapy (mesalamine) in inducing
or maintaining remission in ulcerative colitis or Crohn’s disease
Different brands of probiotics can contain one to 10 billion
colony-forming units (CFUs). As for dosage, a probiotic with
one to two billion CFUs is recommended to maintain a healthy
digestive tract. However, if a person is taking antibiotics or has
symptoms of a bacterial imbalance such as diarrhea, he/she can
take a probiotic with up to 10 billion CFUs until the problem
is resolved. In order to maintain microorganism balance, a
probiotic of one to two billion CFUs daily or every other day
could be taken. To correct a problem (dysbiosis), probiotics
containing 10 billion CFUs could be taken every day for up to
two weeks .
Regarding the dose of probiotics for neonates, probiotic
supplementation in infants should be done carefully, especially
those who are preterm because preterm infants have impaired
immune system, poor nutrition, and frequent exposure to
harmful microorganisms. It is recommended that: Neonates (less
than 32 weeks of gestation): be given 3 x 109 cfu/day extremely
low birth weight infants: be given 1.5 x 109 cfu/day until they
reach enteral feeds of 50-60 ml/kg/day. The probiotic dose
should be diluted in 1.0 to 1.5 mL of breast milk or water .
Not all Probiotics have the same action and function since
they are specific strains. Probiotics are not absolute treatment;
they are mainly adjuvant and could ameliorate inflammation.
There are side effects for probiotics such as bacteremia and
fungemia. What must be finally resolved are the following: The
optimal doses, duration of treatment, comparison of different
strains and different probiotics, single versus combination
probiotics, combination of probiotics with prebiotics, efficacy of
various probiotics in different disease states, safety of probiotics
in debilitated patients, and safety in patients with compromised
gut epithelial integrity. Where probiotics will lead us? Wait and