Antagonistic effects of phenolic extracts of Chokeberry pomace on E. coli O157: H7 but not on probiotic and normal bacterial flora

Abstract

BACKGROUND: Enterohemorrhagic Escherichia coli (EHEC) is still a major foodborne bacterial infectious agent in the USA and causes both diarrheal disease and hemolytic uremic syndrome (HUS). As antibiotic therapy is not an option, appropriate antimicrobial or inhibitor against EHEC colonization/infections is urgently needed. OBJECTIVE: Develop an appropriate natural antimicrobial and stimulate host defense to control foodborne illnesses with EHEC. METHOD: We investigated the role of chokeberry (Aronia melanocarpa) pomace (byproducts) extract (CPE) on growth and survival of EHEC EDL-933, probiotics specifically Lactobacillus, and other common gut bacterial flora including Streptococcus thermophilus, Enterococcus faecalis and Bacillus subtilis. We also tested the effects of CPE on physicochemical properties, host cells-EHEC interactions, and expression of various virulence genes of EHEC. RESULTS:The growth of EHEC EDL-933 was reduced by 4 logs in the presence of 0.5 mg GAE/mL CPE at 5 hr while this concentration promoted the growth of Lactobacillus and common gut bacterial flora, S. thermophillus, E. faealis and B. subtilis. The abilities of EHEC to attach and invade host intestinal epithelial (INT-407) cells were also reduced significantly (p < 0.05) which was supported by alternation physiological properties of EHEC and virulence genes expression. CONCLUSION: These results suggest that CPE has the potential to be an effective therapeutic/preventive for EHEC EDL-933 without affecting the common gut microflora and probiotics.

Antagonistic Mechanism of Metabolites Produced by Lactobacillus casei on Lysis of Enterohemorrhagic Escherichia coli

“…Previously, we also reported that CFCS CLA impaired physicochemical properties of bacterial pathogens such as autoaggregation, surface hydrophobicity, and biofilm formation of several enteric bacterial pathogens more efficiently than CFCS wt (Vu et al, 2009;Peng et al, 2018;Tabashsum et al, 2018). As the physicochemical properties play a major role in pathogenic bacterial adherence to host cells, secretion of effector proteins, and initiate colonization (Sorroche et al, 2012;Cordonnier et al, 2017;Aditya et al, 2019), we also compared the expression of genes which are involved in such physicochemical properties and secretion of proteins in the presence of CFCSs collected from LC wt and LC CLA . Major virulence genes involved in EHEC Type-III secretion system (T3SS), i.e., eaeA, espA espB, espD, tir, and ler are downregulated presumably by the polyunsaturated fatty acid components of CFCSs (Cardenal-Muñoz and Ramos-Morales, 2011;Peng and Biswas, 2017;Peng et al, 2018).…”

“…The effect of the collected metabolites against EHEC EDL933 growth was determined quantitatively in vitro following the method previously described in triplicate (Peng et al, 2015a;Salaheen et al, 2016;Aditya et al, 2019). Briefly, individual culture tubes containing LB broth and one of the CFCSs (CFCS wt , CFCS wt+PF , or CFCS CLA ) in a ratio of 3:1 (v/v) was used as a treatment, where the same ratio of LB and MRS broth was considered as control.…”

“…Using the cDNA (40 ng) as a template, the q-PCR reaction mixture was prepared according to PerfeCTa R SYBR R Green FastMix R protocol (Quanta Biosciences, Beverly, MA, United States) and amplified in an Eco Real-Time PCR system (Illumina, San Diego, CA, United States) with 30 s denaturation at 95 • C, followed by 40 cycles of 95 • C for 5 s, 55 • C for 15 s, and 72 • C for 10 s. The relative expression level of the target genes in treatment was calculated by the comparative log fold change. The C t (cycle threshold) value of target genes in treatment was normalized to the reference gene (Aditya et al, 2019) (all genes used in this study are listed in Table 1) in treatment then the relative expression of the genes was compared between respective treated and untreated conditions (Livak and Schmittgen, 2001).…”

“…Besides, some bacterial infections, including enteric infections with enterohemorrhagic Escherichia coli O157: H7 (EHEC), cannot be treated with traditional synthetic antibiotics because of severe consequences of cytotoxic or adverse effects of the pathogen. For example, antibiotic therapy in EHEC infection can induce the rapid release of Shiga-like toxin (stx) in the gastrointestinal (GI) tract by the death of a vast number of pathogens, which may lead to hemolytic uremic syndrome (HUS) or kidney failure (Cordonnier et al, 2017;Aditya et al, 2019). Further, it also negatively modulates the normal inter-colonic microbial balance which increases the systemic absorption of the toxin (Peng et al, 2015a).…”