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.
Highlights
Infections by Shiga toxin-producing Escherichia coli (STEC) strains are a serious public health concern, resulting in diarrhea, hemorrhagic colitis, and haemolytic uremic syndrome (HUS).Stx is the main virulence factor in STEC strains
Induction of φΔTOX:green fluorescent protein (GFP) by ciprofloxacin and chitosan antibacteriophage effects Lytic induction was triggered in the E. coli C600ΔTOX:GFP strain using ciprofloxacin[9]
Positive detection of phages was observed in intestine homogenates and blood samples of infected mice after ciprofloxacin induction. These results indirectly demonstrate that φΔTOX:GFP is released by the lysogenic bacterial E. coli strain and systemically spread and transduce cells in different mouse organs and tissues after oral infection and lytic induction
Summary
Infections by Shiga toxin-producing Escherichia coli (STEC) strains are a serious public health concern, resulting in diarrhea, hemorrhagic colitis, and haemolytic uremic syndrome (HUS). Stx is the main virulence factor in STEC strains. The stx gene is present in the genome of prophages, which are similar to the bacteriophage lambda found in the lysogenic form of various E. coli strains. We reported that the native promoter of the Stxencoding gene can drive expression of the toxin in eukaryotic cells in both in vivo and in vitro conditions[1,2]. Many questions remain unanswered with regard to the mechanism by which STEC infection causes HUS. We are interested in understanding how Stx enters the systemic circulation and why only very small numbers of bacteria are sufficient to induce HUS in humans[3]
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