It has been almost a year since the world is facing the coronavirus pandemic. The SARS-CoV-2 virus has a huge impact not only on the economy, but above all on human health. Interspecies transmissions of viruses between humans may result in unpredictable pathogenic potential and new transmissible diseases. We are constantly learning about new pathogenic viruses, incl. SARS-CoV-2 or Ebola. The doctors, scientists are on search for the various means and methods against pathogenic viruses. There is also increasing talk of the effectiveness of probiotics and their importance in preventing viral infections.

Probiotic microorganisms show multidirectional, beneficial effects on the human body, confirmed by numerous scientific and clinical studies. Probiotic microorganisms support the maintenance of the intestinal microbiological balance after antibiotic therapy, regulate the digestive tract, strengthen the immune system and help to maintain the psychophysical balance of the body. Probiotic microorganisms also have an antiviral properties.

Recently, a very interesting publication Aravind Sundararaman, Mousumi Ray, P.V. Ravindra i Prakash M. Halami: Role of probiotics to combat viral infections with emphasis on COVID-19 has appeared in Applied Microbiology and Biotechnology. As the authors of the publication write: „Probiotics and their metabolites may also indirectly interfere with the virus by altering the state of cells, stimulating innate and/or adaptive immunity. They exert antiviral activity by (1) direct probiotic–virus interaction, (2) production of antiviral inhibitory metabolites, and (3) stimulation of the immune system.”

The safety of probiotics has been demonstrated by numerous clinical studies. The mechanism of how probiotics work is complicated and still not fully explained. Nevertheless, current evidences show probiotics and probiotic-derived factors have promise for enhancing health benefits and regulation of human homeostasis, including immune health.

Aravind Sundararaman, Mousumi Ray, P.V. Ravindra i Prakash M. Halami are writing about the effectiveness of probiotics and their importance in preventing viral infections, explain: „Lactic acid bacteria (LAB) and their bacteriocins serve as antiviral agents (Al Kassaa et al. 2014). LAB are known to synthesize exopolysaccharides (EPS), which may confer health benefits to people such as immunomodulatory, antitumor, antibiofilm, and antioxidant activities.” The antiviral activity of probiotic bacteria has been confirmed in studies on various pathogenic viruses. Probiotic bacteria have antiviral properties, including: Lactobacillus plantarum, Lactobacillus casei, Lactobacillus rhamnosus, Lactococcus lactis, Bifidobacterium infantis, Bifidobacterium animalis, Bacillus subtilis. However, it should be remembered that the antiviral properties of probiotic microorganisms, like all other properties, are strictly strain-dependent, i.e. specific to one specific strain.

The typical clinical symptoms of COVID-19 include: pneumonia, dry cough, fever, fatigue, myalgia and dyspnea, headache, sore throat, rhinorrhoea and gastrointestinal symptoms. Most of these symptoms are related to the lungs. Immunomodulation in the course of respiratory diseases is mediated by the intestinal microbiota on the gut-lung axis. The gut-lung axis is assumed to be bidirectional. During respiratory infections, commensal microorganisms that are in the intestines stimulate an immune response to local (lungs) and distal (intestines) sites. Probiotic bacteria also could bind to an invading virus, thus inhibiting virus attachment to the host-cell receptor. Probiotic medication helps to fortify mucosal immunity and provide restriction against respiratory viral infection.

As emphasized by the authors of the publication: „Protection from viral infection has shown as a benefit of probiotic action. The probiotics exert their beneficial effects through modulation of host immune responses, maintain gut homeostasis and produce interferon thereby suppressing the virus induced cytokine storm. (…) Immune stimulation through probiotics potentially promote prolonged resistance to virus infections and diseases in humans.”

More research and clinical trials are needed for probiotic administration as an adjuvant therapy for the management of COVID-19 patients. However, there is no doubt that probiotics are effective and of great importance in preventing viral infections.

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