The Anti-Constipation Effect of Bifidobacterium Longum W11 Is Likely Due to a Key Genetic Factor Governing Arabinan Utilization

Recent investigations have highlighted, both experimentally and clinically, that probiotic strains equipped with arabinofuranosidase, in particular abfA and abfB, favor regular intestinal motility, thus counteracting constipation. By analyzing the gene expression and the proliferative response in the presence of arabinan of the probiotic B. longum W11, a strain previously validated as an anti-constipation probiotic, we have speculated that its response mechanism to arabinan can effectively explain its clinical action. Our approach could be used in the future to select probiotics endowed with arabinofuranosidase-related anti-constipation effects.

Selection, Comparative Genomics, and Potential Probiotic Features of Escherichia coli 5C, a pks-Negative Strain Isolated from Healthy Infant Donor Feces

Among the emerging issues in probiotic safety, the possible presence of pks, a gene cluster synthetizing a genotoxin known as colibactin, is one of the most alarming. Indeed, indigenous E. coli strain pks-positive are found in 60% of patients with colorectal cancer, and the most widely used E. coli-based probiotic, known as E. coli Nissle 1917 (DSM 6601), is pks-positive. Starting from 25 potential candidates selected by screening 25 infant stool samples, we have selected an E. coli strain (named 5C, deposited as LMG S-33222) belonging to the phylotype A and having the serovar O173:H1. Having been previously completely sequenced by our group, we have further characterized this strain, demonstrating that it is (i) devoid of the most known potential pathogenic-related genes, (ii) devoid of possible plasmids, (iii) antibiotic-sensitive according to the EFSA panel, (iv) resistant in gastric and enteric juice, (v) significantly producing acetate, (vi) poorly producing histamine, (vii) endowed with a significant in vitro antipathogenic profile, (viii) promoting a significant in vitro immunological response based on IL-10 and IL-12, and (ix) devoid of the pks genes. A comparative genomics versus E. coli Nissle 1917 is also provided. Considering that the other two most commonly used E. coli-based probiotics (E. coli DSM 17252 and E. coli A0 34/86) are respectively pks-positive and alpha-hemolysin-(hly) and cytotoxic necrotizing factor-1-(cnf1) positive, this novel strain (E. coli 5C) is likely the probiotic E. coli strain with the best safety profile available to date for human use.

Draft genome sequence of non-pathogenic Escherichia coli 5C LMG S-33222, isolated from healthy donor feces

We present the genome sequence of Escherichia coli 5C LMG S-33222, a non-pathogenic microorganism with potential probiotic features. The strain was isolated in 2021 from a fecal sample of a healthy Italian infant. The total genome size is 4,712,575 bp with a G + C content of 51%.