Trans-Cinnamaldehyde, Carvacrol, and Eugenol Reduce Campylobacter jejuni Colonization Factors and Expression of Virulence Genes in Vitro

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.

Effects of Sublethal Thymol, Carvacrol, and trans -Cinnamaldehyde Adaptation on Virulence Properties of Escherichia coli O157:H7

“…2). This observation agrees with previously reported studies, wherein soft agar containing sublethal Car, TC, or Eug were found to significantly (P Ͻ 0.05) reduce the motility of S. Typhimurium and C. jejuni (8,22).…”

“…Essential oils (EOs) are gaining popularity in recent years, due to their natural origin, wide-spectrum antimicrobial activities, and generally recognized as safe (GRAS) status for food usage (4). In particular, thymol (Thy), carvacrol (Car), and trans-cinnamaldehyde (TC), the principal compounds of thyme, oregano, and cinnamon EOs, respectively, have been demonstrated to possess good antimicrobial activities against various foodborne pathogens, including E. coli O157:H7 (5), Staphylococcus aureus (6), Salmonella enterica serovar Typhimurium (7), Pseudomonas aeruginosa (3), and Campylobacter jejuni (8).…”

Carvacrol ameliorates acute campylobacteriosis in a clinical murine infection model

“…Carvacrol treatment starting 4 days prior murine infection could sufficiently lower intestinal C. jejuni burdens up to 2 orders of magnitude until day 6 p.i. The antimicrobial properties of carvacrol directed against food-borne pathogens such as C. jejuni [26,29,30,37] Salmonella spp. [37,[43][44][45], Escherichia coli O157:H7 [46] and Bacillus cereus [47,48] have been shown in vitro recently.…”

“…Both, in vitro and in vivo studies revealed that carvacrol application could effectively reduce C. jejuni loads in intestinal samples derived from chicken [25][26][27][28]. Furthermore, carvacrol could effectively reduce virulence gene expression and invasion of C. jejuni into chicken cells [26,29]. Most importantly, the finding that carvacrol application resulted in inhibition of motility and invasive properties of C. jejuni in vitro points towards carvacrol as a promising candidate molecule for the combat of human campylobacteriosis [30].…”

Anti-adhesion activity of phytochemicals to prevent Campylobacter jejuni biofilm formation on abiotic surfaces

“…Furthermore, Sulaeman et al (2012) showed a link between the expression of the cadF gene, which encodes an outer membrane protein, and C. jejuni adhesion. Compounds that reduced the expression of cadF, such as trans-cinnamaldehyde, carvacrol and eugenol, also reduced C. jejuni adhesion to abiotic surfaces (Upadhyay et al 2017;Wagle et al 2019); thus, alterations to the C. jejuni membrane can be considered as one of their mechanisms of antiadhesion action.…”