Campylobacter and Arcobacter species sensitivity to commercial orange oil fractions

Seven orange oil fractions were screened for their ability to inhibit the growth of selected Campylobacter and Arcobacter spp. using the standard agar-disk diffusion assay. Cold pressed (CP) terpeneless Valencia orange oil was found to be the most inhibitory to both Campylobacter jejuni and Campylobacter coli, exhibiting maximum zones of inhibition up to 80+/-0.0 mm. Five-fold concentrated Valencia oil and distilled d-limonene resulted in Campylobacter inhibition zones ranging from 11.0+/-1.4 to 44+/-1.4 mm against both C. jejuni and C. coli. No inhibition of Arcobacter spp. was detected by 6 out of 7 orange fractions except CP terpeneless Valencia orange oil which produced inhibition zones varying from 9.5+/-0.7 to 29+/-1.4 mm. Naturally occurring C. jejuni UAF 244 was isolated from a whole retail chicken, confirmed by hippuricase gene PCR assay, and used to determine antimicrobial capacities of the CP terpeneless Valencia orange oil and limonene when applied on chicken legs and thighs. The two types of chicken parts did not influence the antimicrobial strength of both orange fractions. While the observed reduction of C. jejuni cells attached to the skin varied approximately 1.5 to 2 logarithms compared to the control, the growth inhibition of the bacterial cells by limonene in the rinse increased by 6-fold and complete inhibition without recovery of detectable viable cells occurred when CP Valencia orange oil was applied. The study demonstrated the potential of the selected commercial orange oil fractions to serve as natural antimicrobials against C. jejuni, C. coli, and Arcobacter spp.