New colorimetric aptasensor for rapid on-site detection of Campylobacter jejuni and Campylobacter coli in chicken carcass samples

Campylobacter is the most common cause of infectious intestinal disease, with nearly all cases caused by two species: C. jejuni and C. coli. We recently reported a gold nanoparticle-based two-stage aptasensing platform, which was improved in the present study for the rapid and on-site detection of both C. jejuni and C. coli in food samples. Compared to the previous platform, the improved platform yielded a more obvious colour change from red to purple due to the aggregation of gold nanoparticles, and does not require additional time or a pH optimization step for the aptamers to be adsorbed onto the gold nanoparticles. Using a highly specific aptamer that binds to live C. jejuni and C. coli, the improved aptasensor was highly effective for testing pure culture samples. The accuracy of the newly developed platform was comparable (p = 0.688) to that of the gold-standard detection method of tazobactam-supplemented culture, whereas it was superior to the official agar-based detection method (p = 0.016) in a validation study with 50 naturally contaminated chicken carcass samples. This is the first study on a colorimetric sensor that targets both live C. coli and C. jejuni in naturally contaminated samples. In addition, we provide the first evidence that both morphological status and the amount of Campylobacter present play key roles in the effectiveness of colorimetric detection. Thus, suitable selection of an antibody or aptamer with consideration of the morphological status of pathogens in samples is essential for direct detection without enrichment. Our data suggest that the sensor developed in this study can provide an excellent screening method, with a reduction in the detection time from 48 h to 30 min after enrichment, thus saving time, labour, and cost.