Location: Food and Feed Safety Research
Title: Effects of thymol and diphenyliodonium chloride, inhibitors of amino acid fermentation, against campylobacter in vitro; disruption of campylobacter's amino acid fermentation niche Authors
Submitted to: Proceedings of Allen D Leman Swine Conference
Publication Type: Abstract Only
Publication Acceptance Date: August 17, 2007
Publication Date: September 15, 2007
Citation: Anderson, R.C., Krueger, N.A., Harvey, R.B., Callaway, T.R., Edrington, T.S., Nisbet, D.J. 2007. Effects of thymol and diphenyliodonium chloride, inhibitors of amino acid fermentation, against Campylobacter in vitro; disruption of Campylobacter's amino acid fermentation niche [abstract]. Proceedings of Allen D. Leman Swine Conference. 34:32. Technical Abstract: Approximately 2.4 million cases of human campybacteriosis occur in the U.S. annually, with 80% being foodborne transmitted. Campylobacter are ubiquitous colonizers of the gastrointestinal tract, with prevalence exceeding 80% in swine. Consequently, strategies are sought to reduce carriage of this foodborne pathogen in pigs before processing. Because Campylobacter ferment amino acids rather than sugars, we hypothesized that inhibitors of amino acid fermentation may disrupt this pathogen’s fermentation niche. Two hundred and fifty mL of Bolton broth was inoculated with 0.5 g freshly collected porcine feces and an overnight grown culture (in Bolton broth) of C. jejuni to achieve 1.7 x 10**6 colony forming units (CFU)/mL). This suspension was mixed and distributed (10 mL volumes) under a 100% N2 to 18 x 150 mm crimp-top tubes (in triplicate) preloaded with small volumes (< 0.2 mL) of 100 mM thymol, 1 mM monensin (each in ethanol) and 100 mM diphenyliodonium chloride (DIC, in water). Tubes (n = 3/treatment) were incubated at 37 deg C for 24 h. Campylobacter concentrations were enumerated via plating of samples collected at 0, 6 and 24 h; ammonia accumulations were determined via colorimetric analysis. Tests for effects of treatments were determined by a repeated measures analysis of variance with Tukey’s separation of means. Our results revealed that the inhibitors of amino acid fermentation, thymol and DIC (each at 1 mM), but not monensin (at 0.01 mM), inhibited (P<0.05) recovery of C. jejuni by >4 log10 colony forming units/mL after 6 h and by >6 log10 colony forming units/mL after 24 h of incubation when compared to concentrations measured in control incubations (>6 log10 colony forming units/mL) grown without any inhibitor. Ammonia accumulation was reduced (P<0.05) by >64% in incubations containing thymol or DIC further indicating that fermentation, and subsequent deamination, of amino acids was inhibited. These results reveal a physiological characteristic of Campylobacter that may potentially be exploited to develop interventions.