Introduction

Probiotics is derived from a Greek word meaning “for life”. It refers to a live microorganism or group of microorganisms beneficial for other species, also called “friendly bacteria” or “good bacteria”. According to WHO, probiotics are live microorganisms when administered in adequate amounts manifest multiple health benefits to the host. The first probiotic was reported to be fermented milk consumed by humans. Raw milk and fermented dairy products, such as cheese, yogurt, and fermented products, include Lactobacilli, which are widely present in diets and develop in the gastrointestinal tract shortly after birth¹.

Different Sources of Foods Containing Probiotics.

Probiotics can be either bacteria, molds, or yeasts but mostly they are bacteria belonging to the strains of genera Lactobacillus and Bifidobacterium. However, strains of Bacillus, Pediococcus, and some yeasts (Saccharomyces cerevisiae) have also been found as suitable candidates². Those microbes are only used as probiotics that are considered safe by GRAS because they should be able to dwell in the human body causing no damage. Moreover, scientific evidence must support the health benefits produced by the species. Probiotics are supplemented in the body as an addition to microbiota already established there³. They can be looked at through different dimensions, however, here we will be focusing on two types of bacteria Lactobacilli and Bifidobacterium as model probiotics along with probiotics’ impact on immunity.

Impact of probiotics on the immune system

The human body is home to over 32 billion healthy and non-healthy microbes. Out of which 70-80% compose the body’s immune system. Introducing healthy bacteria to the body is a way of challenging the immune system. The lack of friendly microbes in the body makes the immune system dull and people become prone to autoimmune diseases, allergies, and inflammation. For the body to combat the attack of pathogenic microorganisms, the community of probiotics needs to be well-established. Probiotics have a partnership with immunity to plan and implement strategies to prevent toxins and pathogens from harming the body. They are responsible for stimulating immune cells such as T cells, B cells, macrophages, and NK cells along with cytokines and phagocytic cells to induce cell-mediated, humoral immune response and external barrier mechanisms.

In addition to this, they produce antimicrobial components to manage or destroy large populations of pathogens. Similarly, they produce different molecules such as acetic acid, formic acids, lipopolysaccharides, peptidoglycans, and superantigens to benefit each other or inhibit invaders⁴.

Lactobacillus: A model probiotic

Lactobacillus is a gram-positive, catalase-negative, non-spore-forming, anaerobic, either cocci or rod-shaped bacteria, characterized by lactic acid as the major end product of carbohydrate fermentation. They are abundantly found in the human body in the gut, oral cavity, genital, and urinary systems. Strains belonging to this genus are characterized as safe (GRAS) by the FDA due to their predominance in common foods like cheese, yogurt, and many other fermented foods. They have proven benefits on the host immune system exhibiting competitive exclusion and higher adherence. Some strains produce antibacterial molecules, called bacteriocins to disrupt pathogenic bacteria. For instance, Lactobacillus bulgaricus secretes bulgarican and L. plantarum secretes lactolin⁵.

Nowadays, these species are being used as therapeutic supplements to tackle health complications thus, are available as drugs in the market. They are majorly used for treating diarrhea and other vector-based infections such as rotaviral diarrhea and traveler’s diarrhea⁶. Apart from this, this is taken as medication for a variety of problems such as:

Digestive disorders like Irritable Bowel Syndrome, Crohn’s disease, Necrotizing Enterocolitis
Helicobacter pylori infections
Urinary tract infections like yeast vaginal infections
Autoimmune disorders like Lyme disease and hives
Respiratory infections
Skin disorders like acne, eczema, fever blisters, canker sores

Bifidobacterium

It is also a gram-positive, non-spore-forming, non-motile, catalase-negative, anaerobic bacteria belonging to phyla Actinobacteria that produces acetic acid and lactic acids from carbohydrate fermentation⁷. They are significant components of human and animal gastrointestinal microflora. The first species of Bifidobacterium was isolated from breast-fed infant feces and now there are over 90 known species belonging to this genus. Some of the common strains include B. animalis, B. breve, B. bifidum, B. longum, B. angulatum, etc. It has proven to have a wide range of health benefits to humans such as treating antiviral infections, intestinal infections, decreasing cholesterol levels, cancer risks, and boosting immune systems⁸. Some of its potential health benefits are listed below:

It also treats antibiotic-associated diarrhea as the probiotics containing these strains reduce the duration of diarrhea.
It reduces the symptoms of inflammatory bowel disease and other enteric inflammations⁹
Long-term consumption of Bifidobacterium reduces allergic symptoms in children
It relieves constipation
Administration of these species shows a lower occurrence of necrotizing enterocolitis¹⁰.

References:

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