Novel antimicrobial peptide prevents C. rodentium infection in C57BL/6 mice by enhancing acid-induced pathogen killing

Abstract

Citrobacter rodentium is a Gram-negative, murine-specific enteric pathogen that infects epithelial cells in the colon. It is closely related to the clinically relevant human pathogen, enterohemorrhagic Escherichia coli (EHEC), a leading cause of haemorrhagic colitis and haemolytic uremic syndrome. We have previously reported that a novel antimicrobial peptide, wrwycr, compromises bacterial DNA repair and significantly reduces the survival of acid-stressed EHEC, suggesting an antimicrobial strategy for targeting the survival of ingested EHEC. This study examines the impact of peptide pretreatment on survival of the closely related murine pathogen, C. rodentium, before and after acid stress, using both in vitro and in vivo investigations. Peptide pretreatment of C. rodentium significantly and dramatically increases acid-stress-induced killing in a peptide-dosedependent and time-dependent manner. Reduction in survival rates after brief pretreatment with peptide (25-65 µM) followed by 1 h at pH 3.5 ranges from 6 to 8 log fold relative to untreated C. rodentium, with no detectable bacteria after 65 µM peptide-acid treatment. Using a C57BL/6 mouse model of infection, peptide pretreatment of C. rodentium with wrwycr prior to orogastric gavage eliminates evidence of infection based on C. rodentium colonization levels, faecal scores, colonic histology, faecal microbiome and visual observation of overall animal health. These findings provide compelling evidence for the role of the peptide wrwycr as a potential strategy to control the growth and colonization of enteric pathogens.

Dps Protects Enterohemorrhagic Escherichia coli against Acid-Induced Antimicrobial Peptide Killing

“…The combination peptide-acid treatment, which we previously demonstrated to be effective at ameliorating infection in a C. rodentium mouse model of EHEC infection (10), combines both of these effects and therefore requires two mechanisms of DNA protection though Dps, namely DNA binding and ferroxidase activity (17). This is supported by the enhanced level of bacterial killing seen in the wild-type strain when exposed to peptide-acid treatment, which is exaggerated in the dps mutant, compared to that seen with either acid or peptide treatment alone.…”

“…Our laboratory previously demonstrated that the D-amino acid hexapeptide WRWYCR enhances acid-induced killing of EHEC and ablates infection in a Citrobacter rodentium mouse model of EHEC infection (9,10). WRWYCR has previously been shown to bind to Holliday junctions during bacterial DNA repair and to prevent their resolution, thereby causing bacterial cell death (11,12).…”