The Effect of Thymol-B-D-Glucopyranoside on the Reduction of Campylobacter Species in Food-Producing Animals
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Campylobacter are a leading cause of bacterial derived foodborne illness. Thymol is a natural product that reduces survivability of Campylobacter in vitro. Results from animal studies, however, indicate that absorption or degradation within the stomach and small intestine may preclude delivery of thymol to the cecum and large intestine, the main sites of Campylobacter colonization. Presently, we compared the anti- Campylobacter activity of thymol against that of thymol--D-glucopyranoside (-Dthymol), the latter suspected to be resistant to degradation and absorption in the proximal alimentary tract lacking -glycosidase activity. When treated with 1 mM thymol, the survivability of Campylobacter coli and jejuni in vitro was reduced by 3.41 to 6.87 log_10 CFU mL-1 after 48-h pure culture and after co-culture, respectively. In the presence of a -glycosidase-expressing Parabacteroides distasonis. Conversely, the survivability of C. coli and C. jejuni was reduced by 3.72 and 4.30 log_10 CFU mL-1, respectively, in cocultures treated with -D-thymol, but not in pure cultures similarly treated. When tested in mixed cultures of porcine or bovine fecal microbes possessing endogenous - glycosidase, C. coli and C. jejuni survivability was reduced by 3.26 and 2.50 log_10 CFU mL-1, respectively, whether treated with thymol or -D-thymol. In mixed populations of avian crop and cecal microbes, C. jejuni survivability was reduced 1.41 to 2.32 log_10 CFU mL-1 whether treated with thymol or -D-thymol. Thymol and -D-thymol inhibited ammonia accumulation in mixed populations of porcine and mixed bovine fecal microbes which is consistent with free thymols purported role as a deaminase inhibitor. Conversely, thymol and -D-thymol did not affect ammonia accumulation in mixed populations of avian gut microbes implicating population specific effects of these compounds. -D-thymol, but not thymol, reduced accumulation of fermentation acids indicating the conjugate inhibited fermentation which may limit its application to the last meal or last few meals before harvest. Oral administration of 150 mol -D-thymol reduced C. jejuni in avian crop, but not in cecal contents; treatment with thymol was ineffective. These results indicate that -D-thymol, or similar -glycosides, may be a suitable candidate to escape absorption and degradation within the proximal alimentary and retain its anti-Campylobacter properties. Further research is needed to reduce such technology to practice.
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