Location: Food Safety and Enteric Pathogens ResearchTitle: Comparative evaluation of antimicrobial activity of human granulysin, bovine and porcine NK-lysins against Shiga toxin-producing Escherichia coli O157:H7
|BIERNBAUM, ERIKA - Oak Ridge Institute For Science And Education (ORISE)|
Submitted to: Meeting Abstract
Publication Type: Abstract Only
Publication Acceptance Date: 3/3/2023
Publication Date: N/A
Technical Abstract: Shiga toxin-producing Escherichia coli (STEC) O157:H7 (O157), a foodborne pathogen, causes disease ranging from hemorrhagic colitis to hemolytic uremic syndrome and kidney failure in humans, while remaining harmless to its primary reservoir, cattle. The severity of the human disease, and a global emergence of antibiotic resistant STEC highlights the need for effective, non-antibiotic, pre-harvest strategies to reduce O157 in cattle, the principal source of human infection. Towards this goal, three synthetic antimicrobial peptides (AMPs), human granulysin (hGRNL), bovine NK-lysin (bNK2A), and porcine NK-lysin (pNKL), were tested in vitro against O157 isolates. As expected, circular dichroism spectroscopy findings were consistent with a predominantly a-helical conformation for all three AMPs in an environment mimicking bacterial outer surface or liposaccharides. The minimum inhibitory concentrations (MIC) of hGRNL, bNK2A, and pNKL in Müeller-Hinton broth (Cation-Adjusted), as determined by Clinical and Laboratory Standard Institute broth microdilution method, were 200, 12.5, and 6.25 µM, respectively. Minimum bactericidal concentrations were identical to MIC, and neither AMPs appeared to induce Shiga toxin expression in O157 when tested at MIC. Propidium iodide uptake assay revealed faster O157 membrane damage or killing kinetics with bNK2A and pNKL as compared to hGRNL. Nonetheless, transmission electron microscopy demonstrated that all three AMPs mediated damage to O157 membranes. In contrast, the three AMPs showed minimal cytotoxicity (<2%) against cattle red blood cells at tested concentrations (0.39-50 µM). Overall, our results demonstrate the potential for bNK2A and pNKL to be further developed into novel non-antibiotic agents to reduce O157 shedding in cattle.