Role of bacteriophages in STEC infections: new implications for the design of prophylactic and treatment approaches

Abstract

Shiga toxin (Stx) is considered the main virulence factor in Shiga toxin-producing Escherichia coli (STEC) infections. Previously we reported the expression of biologically active Stx by eukaryotic cells in vitro and in vivo following transfection with plasmids encoding Stx under control of the native bacterial promoter. Since stx genes are present in the genome of lysogenic bacteriophages, here we evaluated the relevance of bacteriophages during STEC infection. We used the non-pathogenic E. coli K12 strain carrying a lysogenic 933W mutant bacteriophage in which the stx operon was replaced by a gene encoding the green fluorescent protein (GFP). Tracking GFP expression using an In Vivo Imaging System (IVIS), we detected fluorescence in liver, kidney, and intestine of mice infected with the recombinant E. coli strain after treatment with ciprofloxacin, which induces the lytic replication and release of bacteriophages.In addition, we showed that chitosan, a linear polysaccharide composed of D-glucosamine residues and with a number of commercial and biomedical uses, had strong anti-bacteriophage effects, as demonstrated in vitro and in vivo. These findings bring promising perspectives for the prevention and treatment of hemolytic uremic syndrome (HUS) cases.

Pathogenomes of Atypical Non-shigatoxigenic Escherichia coli NSF/SF O157:H7/NM: Comprehensive Phylogenomic Analysis Using Closed Genomes

“…Therapeutic use of certain antibiotics is known to induce Stx 2a phages (Huang et al, 1987;Mead and Griffin, 1998;Zhang et al, 2000;Zimmerhackl, 2000;Wong and Brandt, 2002;McGannon et al, 2010;Wong et al, 2012;Amorim et al, 2014;Rahal et al, 2015). Strains were cured of stx by inducing the Stx-phages with Mitomycin C (MMC), a potent Stx 2a phage inducing agent that triggers the RecA-mediated SOS-response (Fuchs et al, 1999;Kimmitt et al, 2000;Los et al, 2009;Imamovic and Muniesa, 2012).…”

Comparable stx2a expression and phage production levels between Shiga toxin‐producing Escherichia coli strains from human and bovine origin

“…Stx phages play an important role in disease, STEC evolution and ecological fitness. Synthesis and secretion of these toxins, particularly Stx2 type, are coupled with the lytic cycle of such phages whose direct role in disease pathogenesis has been also proposed (Amorim et al, ). Additionally, toxin production can be amplified by the horizontal transfer of Stx phages to commensal E. coli (Gamage et al, ).…”

Cationic Antimicrobial Peptides Inactivate Shiga Toxin-Encoding Bacteriophages

“…We have previously observed a dramatical decrease of GFP expression in vivo in mice treated with chitosan after infection with a non-pathogenic E. coli strain containing a mutant bacteriophage in which the gene of stx was replaced by gfp sequence (Amorim et al, 2014 ).…”

“…Previously, we showed that chitosan has anti-bacteriophage activity in vitro and in vivo (Amorim et al, 2014 ). Chitosan is a cationic linear polysaccharide polymer obtained after the deacetylation of chitin; this polymer has been widely-used as an antimicrobial agent against several microorganisms (Kong et al, 2010 ).…”

“…In order to evaluate whether these sequences could affect bacteriophage infection we tested seven previously designed cAMPs (Faccone et al, 2014 ; Hollmann et al, 2016 ; Maturana et al, 2017 ) as potential anti-bacteriophage agents. To analyze the effect of these peptides, we used them to inactivate a previously reported mutant bacteriophage (ϕΔTOX:GFP) in which the stx operon has been replaced by a gene encoding for the green fluorescent protein (GFP) (Amorim et al, 2014 ). Five of these peptides were previously analyzed and displayed antimicrobial activity in different bacterial strains and structure as alpha helix in contact with lipid membranes (P5, P8, P8.1, P2, and P6.2).…”