Safety assessment of Weissella confusa - A direct-fed microbial candidate.

ABSTRACT

Weissella confusa is part of the lactic acid bacteria genera and a member of an autochthonous microbiota of humans and livestock. W. confusa has been proposed to have potential as a direct-fed microbial product, however, there is a lack of studies assessing its safety. A toxicological safety assessment of W. confusa was performed using a battery of in vitro, ex vivo and in vivo studies, testing for genotoxicity, skin and eye irritation and general toxicity. The bacterial reverse mutation (Ames) study did not reveal any genotoxicity in the presence and absence of metabolic activation (S9) at concentrations up to 5000 µg/mL. Moreover, an in vivo mammalian erythrocyte micronucleus study did not reveal any biologically relevant or statistically significant increases in the frequency of micronucleated polychromatic erythrocytes in mice, when tested at concentrations up to 2000 mg/kg body weight. W. confusa did not exert any skin irritation potential when tested in reconstructed skin membranes. When tested for eye irritation using an ex vivo model of isolated chicken eyes, mild irritation was observed. The 90-day sub-chronic oral toxicity (gavage) study was performed using Sprague Dawley rats at concentrations up to 92 × 108 cfu/kg body weight/day (nominal). The results showed that W. confusa were well tolerated, and no signs of toxicity were seen. The No Observed Adverse Effect Level (NOAEL) for both female and male animals was the highest concentration administered, 92 × 108 cfu/kg body weight/day (nominal). In conclusion, the toxicological studies performed confirmed W. confusa to be safe, making it a good candidate as a direct-fed microbial product.