COVID-19 is an acute respiratory infection accompanied by pneumonia caused by severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2), which has affected millions of people globally. To date, there are no highly efficient therapies for this infection. Probiotic bacteria can interact with the gut microbiome to strengthen the immune system, enhance immune responses, and induce appropriate immune signaling pathways. Several probiotics have been confirmed to reduce the duration of bacterial or viral infections. Immune fitness may be one of the approaches by which protection against viral infections can be reinforced. In general, prevention is more efficient than therapy in fighting viral infections. Thus, probiotics have emerged as suitable candidates for controlling these infections. During the COVID-19 pandemic, any approach with the capacity to induce mucosal and systemic reactions could potentially be useful. Here, we summarize findings regarding the effectiveness of various probiotics for preventing virus-induced respiratory infectious diseases, especially those that could be employed for COVID-19 patients. However, the benefits of probiotics are strain-specific, and it is necessary to identify the bacterial strains that are scientifically established to be beneficial.

In this study, chemical composition, antioxidant and antimicrobial activity of the essential oil of Nepeta cataria L., a native plant that grows in Lorestan region of Iran, were studied. Chemical constituents of the essential oil were identified by means of gas chromatography/mass spectrometry (GC/MS) and the relative content of each constituent was determined by area normalization. Disc diffusion and broth microdilution assays were used for in vitro antimicrobial screening. Antioxidant activity was employed by 2,2-diphenyl-1-picrylhydrazyl (DPPH) free-radical scavenging. The predominant bioactive ingredients with high percentage in N. Cataria essential oil was 4a-α, 7-α, 7a-β-Nepetalactone (53.87%). The essential oil's IC50 value of 80.62 μg / mL in the DPPH assay, could be regarded as its strong antioxidant potential. The antibacterial activities of the essential oil were screened and compared against dozen important human pathogens. The essential oil showed good antibacterial activity, especially on Salmonella spp.. The biggest diameters of inhibition zones (29 mm) was recorded for Salmonella typhi and Salmonella paratyphi A showed the lowest MIC (160 μg / mL).

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Background: Dracocephalum kotschyi Boiss is a herb with wide-spread applications. Lorestan traditional healers have applied it for the treatment of rheumatoid diseases and stomach disorders. Materials and methods: Hydrodistillation process was used for essential oil extraction, the extracted essential oil was then analyzed through combination of capillary GC-FID, GC-MS and RI. The in vitro antimicrobial, antioxidant and cytotoxic activities of this essential oil were examined. Results indicate that the essential oil has a broad range of antimicrobial activity against all of the tested microorganisms. Results: The 50% of cytotoxic concentrations was 26.4 μg/ml and 4266.7 μg/ml for Hela cells and human lymphocytes, respectively. The oil cytotoxicity against the human tumor cell line was far higher than the amount required for human healthy cells. Conversely, the essential oil's IC 50 value of 49.2 μg/ml in the DPPH assay, could be regarded as its strong antioxidant potential. Conclusion: According to the data obtained, it can be concluded that D. kotschyi essential oil could be applied as a safe antibacterial and antioxidant agent for food and pharmaceutical purposes.

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