Abstract
Campylobacter jejuni is one of the leading causes of foodborne illness worldwide. C. jejuni is commonly found in poultry. It is the most frequent cause of contamination and thus resulting in not only public health concerns but also economic impacts. To test for this bacterial contamination in food processing plants, this study attempted to employ a simple and rapid detection assay called loop-mediated isothermal amplification (LAMP). The best cutoff value for the positive determination of C. jejuni calculated using real-time LAMP quantification cycle (Cq) was derived from the receiver operating characteristic (ROC) curve modeling. The model showed an area under curve (AUC) of 0.936 (95% Wald CI: 0.903–0.970). Based on Youden’s J statistic, the optimal cutoff value which had the highest sensitivity and specificity from the model was calculated as 18.07. The LAMP assay had 96.9% sensitivity, 95.8% specificity, and 93.9 and 97.9% positive and negative predictive values, respectively, compared to a standard culture approach for C. jejuni identification. Among all non-C. jejuni strains, the LAMP assay gave each of 12.5% false-positive results to C. coli and E. coli (1 out of 8 samples). The assay can detect C. jejuni at the lowest concentration of 103 CFU/mL. Our results suggest a preliminary indicator for the application of end-point LAMP assays, such as turbidity and UV fluorescence tests, to detect C. jejuni in field operations. The LAMP assay is an alternative screening test for C. jejuni contamination in food samples. The method provides a rapid detection, which requires only 9 min with a cutoff value of Cq. We performed the extraction of DNA from pure cultures and the detection of C. jejuni using the LAMP assay within 3 h. However, we were not able to reduce the time for the process of enrichment involved in our study. Therefore, we suggest that alternative enrichment media and rapid DNA extraction methods should be considered for further study. Compared to other traditional methods, our proposed assay requires less equipment and time, which is applicable at any processing steps in the food production chain.
Highlights
IntroductionCampylobacteriosis is an infectious disease caused by bacteria belonging to the genus
Campylobacteriosis is an infectious disease caused by bacteria belonging to the genusCampylobacter, most notably C. jejuni and C. coli [1]
This study provided a practical idea of loop-mediated isothermal amplification (LAMP) assay application by optimizing reaction temperature to be compatible with the commercial LAMP reaction kit
Summary
Campylobacteriosis is an infectious disease caused by bacteria belonging to the genus. Campylobacter, most notably C. jejuni and C. coli [1]. Among the Campylobacter strains discovered to date, C. jejuni is one of the most frequently discovered predisposing causes of bacterial foodborne diarrheal disease worldwide and is frequently found causing contamination in food sources, such as poultry meat, unpasteurized milk, and drinking water, or cross-contamination of other foods by these items [3–6]. It is estimated that Campylobacter spp. cause 500 million infections in the world every year [7]. According to the United States Food-Borne Diseases Active Surveillance Network (2005–2018), Campylobacter infections had the greatest yearly incidence of 19.5 per 100,000 population, followed by Salmonella (18.3), and Shiga toxin-producing Escherichia coli (STEC; 5.9) [8]. It is estimated that in the United States, Campylobacteriosis affects 1.3 million people a year, and in Canada, there are over 200,000 cases reported each year [9,10]
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