Abstract
Campylobacter jejuni is a major foodborne pathogen that causes severe gastroenteritis in humans characterized by fever, diarrhea, and abdominal cramps. In the human gut, Campylobacter adheres and invades the intestinal epithelium followed by cytolethal distending toxin mediated cell death, and enteritis. Reducing the attachment and invasion of Campylobacter to intestinal epithelium and expression of its virulence factors such as motility and cytolethal distending toxin (CDT) production could potentially reduce infection in humans. This study investigated the efficacy of sub-inhibitory concentrations (SICs, concentration not inhibiting bacterial growth) of three GRAS (generally recognized as safe) status phytochemicals namely trans-cinnamaldehyde (TC; 0.005, 0.01%), carvacrol (CR; 0.001, 0.002%), and eugenol (EG; 0.005, 0.01%) in reducing the attachment, invasion, and translocation of C. jejuni on human intestinal epithelial cells (Caco-2). Additionally, the effect of these phytochemicals on Campylobacter motility and CDT production was studied using standard bioassays and gene expression analysis. All experiments had duplicate samples and were replicated three times on three strains (wild type S-8, NCTC 11168, 81–176) of C. jejuni. Data were analyzed using ANOVA with GraphPad ver. 6. Differences between the means were considered significantly different at P < 0.05. The majority of phytochemical treatments reduced C. jejuni adhesion, invasion, and translocation of Caco-2 cells (P < 0.05). In addition, the phytochemicals reduced pathogen motility and production of CDT in S-8 and NCTC 11168 (P < 0.05). Real-time quantitative PCR revealed that phytochemicals reduced the transcription of select C. jejuni genes critical for infection in humans (P < 0.05). Results suggest that TC, CR, and EG could potentially be used to control C. jejuni infection in humans.
Highlights
The foodborne pathogen Campylobacter is the leading cause of bacterial gastroenteritis in humans resulting in an estimated 96 million annual infections globally (Kirk et al, 2015)
The present study investigated the efficacy of subinhibitory concentrations (SICs, concentrations of compounds not inhibitory to bacterial growth) of TC, CR, and EG in reducing C. jejuni attachment, invasion, and translocation of human intestinal epithelial cells (Caco-2), and production of virulence factors in vitro
Similar results were obtained with C. jejuni NCTC 11168 (Figure 1B) and C. jejuni 81–176 (Figure 1C) where all the phytochemical treatments significantly reduced pathogen motility
Summary
The foodborne pathogen Campylobacter is the leading cause of bacterial gastroenteritis in humans resulting in an estimated 96 million annual infections globally (Kirk et al, 2015). Reducing the attachment and invasion of C. jejuni on intestinal epithelial cells and production of virulence factors such as motility and CDT could potentially control Campylobacteriosis in humans Antibiotics such as macrolides (erythromycin, clarithromycin), and fluoroquinolones (ciprofloxacin, levofloxacin, moxifloxacin) are commonly used for treating Campylobacter infections in humans (Blaser and Engberg, 2008); there have been reports of development of resistance to these drugs (Engberg et al, 2001; Payot et al, 2006; Luangtongkum et al, 2009; Cha et al, 2016; Olkkola et al, 2016) and several resistance genes have been discovered in Campylobacter spp. This increase in antibiotic resistance along with reports of adverse drug reactions in patients (Periti et al, 1993; Thong and Tan, 2011) has fueled research exploring the potential of various antibiotic alternatives to combat Campylobacter infections in humans
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