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United States Department of Agriculture

Agricultural Research Service

Research Project: MICROBIAL COMMUNITIES AND INTERACTIONS AND THEIR IMPACT ON FOOD SAFETY

Location: Molecular Characterization of Foodborne Pathogens

Title: Nonpeptidic mimics of host defense proteins as antimicrobial agents for E. coli O104:H4, campylobacter spp. and other foodborne pathogens

Authors
item Mithal, Sid -
item Chen, Chin-Yi
item Scott, Richard -

Submitted to: Meeting Abstract
Publication Type: Abstract Only
Publication Acceptance Date: June 18, 2012
Publication Date: September 9, 2012
Citation: Mithal, S., Chen, C., Scott, R. 2012. Nonpeptidic mimics of host defense proteins as antimicrobial agents for E. coli O104:H4, campylobacter spp. and other foodborne pathogens. Meeting Abstract. Poster F-1494.

Technical Abstract: Background: Foodborne illness is a serious public health problem. According to the U.S. Food and Drug Administration Campylobacter jejuni is the leading cause of bacterial diarrheal illness in the United States, causing more disease than Shigella spp. and Salmonella spp. combined. The CDC estimates more than 2.4 million people are affected by Campylobacter each year, leading to 124 deaths. E. coli O104:H4 is the Shiga-toxin producing enteroaggregative strain that was responsible for infecting over 3,200 people, killing 50, during a foodborne outbreak in Europe in 2011. PolyMedix has developed small nonpeptidic mimics of host defense proteins (HDP) as antimicrobial agents. The lead compound, PMX30063, is under clinical study for the treatment of staphylococcal infections. A panel of the most prevalent foodborne pathogens, including 8 strains of Campylobacter (4 C. jejuni and 4 C. coli) and 2 clinical isolates of E. coli O104:H4, was screened against a set of structurally-diverse HDP mimics for MICs and cytotoxicity against mammalian cells. Killing kinetics were determined for the most active compounds. Methods: Minimum inhibitory concentrations (MICs) were determined by broth microdilution assays under standard CLSI conditions. Minimum bactericidal concentrations (Campylobacter only) were determined by colony counts. A bioreduction assay was used to quantify cytotoxicity (EC50) in two mammalian cell lines, transformed human liver cells (HepG2) and mouse fibroblasts (3T3). Time-kill (TK) assays were performed over 24 hours and defined as a 3 log10 reduction in CFU/mL from the initial inoculum. Results: A total of 209 HDP mimics were screened for MICs against 2 ATCC strains of E. coli (1 ETEC and 1 O157:H7 strain), S.enterica, S. dysenteriae, L. monocytogenes, Y. enterocolitica, V. parahaemolyticus, and V. vulnificus. Prioritized compounds were screened against 4 C. jejuni, 4 C. coli, and 2 E. coli O104:H4 isolates. All 23 compounds tested were highly active (MIC = 2µg/mL) and bactericidal against both species. Six select compounds were rapidly bactericidal in < 2 hours at 5X MIC for the 4 Campylobacter strains tested in TK assays. All 24 compounds screened against both E. coli O104:H4 strains demonstrated potent activity (MIC= 3.13). Three of 4 compounds selected for killing kinetics were rapidly bactericidal in = 3.3 hours at 2X MIC against the isolate tested. Conclusions. Structurally-diverse HDP mimics have potent and rapid bactericidal activity against foodborne pathogens and low cytotoxicity. These leads are promising candidates for further development.

Last Modified: 11/22/2014
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