Effects of thymol and diphenyliodonium chloride against Campylobacter spp. during pure and mixed culture in vitro

Aims: To determine if the purported deaminase inhibitors diphenyliodonium chloride (DIC) and thymol reduce the growth and survivability of Campylobacter. Methods and Results: Growth rates of Campylobacter jejuni and Camp. coli were reduced compared to unsupplemented controls during culture in Muellar-Hinton broth supplemented with 0 center dot 25 mu mol DIC or thymol ml<SU-1</SU but not with 0 center dot 01 mu mol monensin ml<SU-1</SU or 1% ethanol. Recovery of Camp. jejuni and Camp. coli was reduced > 5 log(10) CFU from controls after 24 h pure culture in Bolton broth supplemented with 0 center dot 25 or 1 center dot 0 mu mol DIC ml<SU-1</SU or with 1 center dot 0 mu mol thymol ml<SU-1</SU. Similarly, each test Campylobacter strain was reduced > 3 log(10) CFU from controls after 24 h mixed culture with porcine faecal microbes in Bolton broth supplemented with 0 center dot 25 or 1 center dot 0 mu mol DIC ml<SU-1</SU or with 1 center dot 0 mu mol thymol ml<SU-1</SU. Treatments with 0 center dot 25 mu mol thymol ml<SU-1</SU, 0 center dot 01 mu mol monensin ml<SU-1</SU or 1% ethanol were less effective. Ammonia production during culture or incubation of cell lysates was reduced by 0 center dot 25 or 1 center dot 0 mu mol DIC ml<SU-1</SU but only intermittently reduced, if at all, by the other treatments. Conclusions: Diphenyliodonium chloride and thymol reduced growth, survivability and ammonia production of Camp. jejuni and Camp. coli. Significance and Impact of the Study: Results suggest a potential physiological characteristic that may be exploited to develop interventions.