Lactobacilli as an PROBIOTIC

The term probiotics is derived from the Greek word “pro” means for and “bio” means life and had assumed several meanings over the years. The term “Probiotics” was first introduced in 1953 by Kollath. Contrasting antibiotics, Probiotics were defined as “microbially derived factors that stimulate the growth of other microorganisms.

L.acidophilus at 100x view

Lilly and Stillwell were another one to introduce the term probiotics in the year 1965 to describe the growth promoting factors produced by the microorganisms. Probiotics are live microbial food supplements that beneficially affect the host by improving its microbial balance (Fuller, 1989; Forestier et al., 2001). According to Reid et al. (2003) probiotics are live microorganisms which when administered in adequate amounts, confers a health benefit on the host.

Probiotics are usually defined as microbial food supplements with beneficial effects on the consumers. The microbial population of gut depends upon the gut flora and 3 major factors:

·         Probiotic bacteria,

·         Pathogenic bacteria and

·         Non digestible food i.e. prebiotics on which probiotics feed.

Probiotics mainly consist of lactic acid producing bacteria (Lactobacilli, Streptococci, Enterococci and Lactococci). Bifidobacteria, Bacillus species, yeasts like Saccharomyces species too find a place in the long list of probiotics. The mode of ingestion is either through food or in a non food format. The probiotics generally subsist in the stomach or intestinal tract.

Microscopic  view of L.acidophilus

Most probiotics fall into the group of organisms known as lactic acid producing bacteria (LAB) and are normally consumed in the form of yogurt and other fermented foods. The LAB, a group of Gram +ve bacteria, consists of several species including the genera Lactobacillus, Lactococcus, Leuconostac, Pediococcus, Aerococcus and Bifidiobacterium. With the LAB, the genus Lactobacillus is the most widely encountered for probiotics. They are normal inhabitants of human intestine and vagina. They are non-spore forming and non- flagellated rods either aerotolerant or anaerobic and strictly fermentative. The GI tract serves as an interface between the gut and immune system, with the intestinal lining functioning as a barrier, decreasing the passage of bacteria from the gut into the bloodstream. Lactobacilli, can preferentially occupy a space or a biofilm that would otherwise be colonised by a pathogen.

This “beneficial bacteria” create an acidic environment that inhibits the intestinal growth of pathogenic bacteria, yeast, and fungi. “Test tube studies have shown that L. acidophilus can and will inhibit the growth, not treat of Candida albicans. It has also been suggested that L. acidophilus may have potential antibiotic effects of its own” (Hartland, 1994). Probiotics do produce a natural antibiotic-like substance called bacteriocin, which helps to eliminate unwanted coliforms. It is necessary that all the strains must be carefully and thoroughly studied prior to their utilization in humans or animals and should be having confirmed generally regarded as safe (GRAS). The following are some of the properties, the probiotics should possess:

1. Colonization or adhesion properties.
2. Human origin.
3. Good in vitro development.
4. Ability of cells to produce metabolites and enzymes.

5. Stability in gastric juices and bile.
6. Production of antimicrobial substances.
7. Safe for clinical use.
8. Antagonistic action against noted pathogenic bacteria and / or viruses.
9. Factors that influence the strain survival during / after administration.

10. No adverse interactions with host especially, in terms of pathogenicity.

Several selection criteria have been used for novel probiotic strains, which can be summarized into three groups:

·         Safety,

·         Functional and

·         Technological aspects (Saarela et al., 2000).

Besides health effects probiotics play an important role in food industry. Probiotics have been employed as a food adjunct to form neutraceuticals. In addition to health beneficial effects probiotics can also act as Biopreservative. Because of their inhibitory effect, selected probiotic lactobacilli may be used as biological preservative.

 Medicinal advantages             

            A lot of studies revealed the medicinal advantages of Probiotics. These are:

·         Mechanisms of bacterial adhesion, competitive colonization of bioflim, and thus has possible effects on Immunomodulation.

·         Several in vitro and in vivo experiments on antagonism of different Lactobacillus strains against Helicobacter pylori and Clostridium difficile, Campylobacter jejuni, Escherischia coli were performed. All tested human Lactobacillus strains were able to inhibit the growth of all strains of anaerobic human gastrointestinal pathogens.

·         In addition, bacteriocins have properties such as antitumour and anticholestrol activity.

·         Lactic acid bacteria in the gastrointestinal tract are capable of delivering enzymes and other substances into the intestine which possibly help to control intestinal flora.

·         Clinical trials have demonstrated that probiotics may decrease the incidence of respiratory tract infections (Hatakka et al., 2001) and dental caries in children (Nase et al., 2001).