Novel saltatory rolling circle amplification assay for rapid and visual detection of Campylobacter jejuni in chicken meat

Campylobacter jejuni is a widespread zoonotic foodborne pathogen and one of the major concerns in the poultrybased food industry. There is a need for a rapid, robust and equipment free detection system for C. jejuni as the conventional culture method is labour and resource-intensive. In this study, we have developed a simple saltatory rolling circle amplification (SRCA) assay integrating a cost-effective three-step centrifugation-based DNA extraction method for rapid and visual detection of C. jejuni in chicken meat. The specificity of the SRCA assay was established by using 17 C. jejuni and 18 non-C. jejuni strains. SRCA, end-point and real-time PCR were able to detect 50 fg, 5 pg and 500 fg C. jejuni DNA/tube, respectively. In the artificial-spiking study conducted in C. jejuni-free chicken meat, a limit of detection (LoD) of 3 log CFU/g and 2 log CFU/g were attained in 120 min (without enrichment) and 14 h (with 12 h enrichment), respectively. The LoD of the SRCA assay was 10- and 100-fold better than the end-point and real-time PCR, respectively. Therefore, keeping the end-user of resourcelimited food analysis laboratories in mind, we have successfully developed a SRCA assay for rapid and accurate detection of C. jejuni in chicken meat.