The controversial nature of the Weissella genus: technological and functional aspects versus whole genome analysis-based pathogenic potential for their application in food and health

Abstract

Despite the use of several Weissella (W.) strains for biotechnological and probiotic purposes, certain species of this genus were found to act as opportunistic pathogens, while strains of W. ceti were recognized to be pathogenic for farmed rainbow trout. Herein, we investigated the pathogenic potential of weissellas based on in silico analyses of the 13 whole genome sequences available to date in the NCBI database. Our screening allowed us to find several virulence determinants such as collagen adhesins, aggregation substances, mucus-binding proteins, and hemolysins in some species. Moreover, we detected several antibiotic resistance-encoding genes, whose presence could increase the potential pathogenicity of some strains, but should not be regarded as an excluding trait for beneficial weissellas, as long as these genes are not present on mobile genetic elements. Thus, selection of weissellas intended to be used as starters or for biotechnological or probiotic purposes should be investigated regarding their safety aspects on a strain to strain basis, preferably also by genome sequencing, since nucleotide sequence heterogeneity in virulence and antibiotic resistance genes makes PCR-based screening unreliable for safety assessments. In this sense, the application of W. confusa and W. cibaria strains as starter cultures or as probiotics should be approached with caution, by carefully selecting strains that lack pathogenic potential.

Ability of a Wild Weissella Strain to Modify Viscosity of Fermented Milk

“…suggest their ability to adapt to different environment and different sugars availability (Abriouel et al, 2015). However, to the best of the authors' knowledge, there are no specific literature data on W. minor ability to ferment milk, but at the same time, some data are available about the inability W. confusa and Weissella cibaria to use lactose and galactose (Quattrini et al, 2019).…”

“…Furthermore, several Weissella species are being extensively studied for their ability to produce significant amounts of extracellular polysaccharides (EPS), which can be used as prebiotics or in food industries with different technological applications (Abriouel et al, 2015).…”

Why Are Weissella spp. Not Used as Commercial Starter Cultures for Food Fermentation?

“…W. ceti is considered to be a pathogen which infects fish and rainbow trout [193,194]. Genome sequence analysis of W. ceti strains revealed the presence of several virulence factors and antibiotic resistance genes [195], which comforts its potential pathogenicity. To the best of our knowledge, no study reported infections associated W. ceti in humans.…”

In vitro assessment of potential probiotic characteristics of indigenous Lactococcus lactis and Weissella oryzae isolates from rainbow trout ( Oncorhynchus mykiss Walbaum)

“…With this regard, they can be considered as safe LAB. However, Abriouel et al (2015) showed the presence of genes coding for two aggregation substances ( Asa1/PrgB ) in W. oryzae SG25.…”