Possible correlation between the probiotic activity of bacterial honey isolates and the in vitro inhibition of coronavirus 2 replication responsible for acute respiratory syndromes

Various strategies, like those using vaccines and antibiotics, have been examined for the prevention and treatment of virus's diseases, but until this moment infection control is not at sufficient level. Exopolysaccharides, especially from probiotics, became one of the most innovative approaches for antiviral agents. This research tried to highlight the effect of a probiotic polysaccharide, such as levan, in COVID-19 prevention. Accordingly, 5 levans types previously obtained from bacterial honey isolates were tested against COVID-19. The most promising result was recorded with levans from Pseudomonas aeruginosa HI1 (levAE) and Bacillus subtilis 9A (lev9A). The lowest cytotoxicity was obtained from lev9A (CC50=5.567e+006 mg/ml) and the most promising IC50 was obtained by levAE (10.75 mg/ml) followed by lev13M (142.5 mg/ml) then lev9A (1299 mg/ml). The dialysis process of levAE greatly affected the virus inhibition activity (IC50 of levAE/D =7.773e+006 mg/ml). Pseudomonas aeruginosa HI1 and Bacillus subtilis 9A were highly tolerant to the acidic (pHs 2, 3) and alkaline conditions (pHs 9, 11). Moreover, when incubated with 0.3 bile salt for 24h, their surviving rates recorded 94% and 100% respectively. H2O2 tolerance showed 77% surviving of Pseudomonas aeruginosa HI1 and 100% surviving of Bacillus subtilis 9A. The blood hemolysis and the antibiotics sensitivity tests confirmed the isolate's safety. The hypothesis that the isolates adhere to the lung cells, could explain the ability of the isolates and their levans to inhibit covid-19 replication.