Rapid and Simultaneous Detection of Campylobacter and Salmonella in Poultry Samples Using Magnetic Nanobeads and Quantum Dots Based Fluorescent Immunosensor

Introduction: Campylobacter and Salmonella are the most important bacterial pathogens associated with foodborne diseases caused by consuming undercooked poultry or handling raw poultry and poultry products. C. jejuni and Salmonella cause 2.4 million and over 1 million cases of foodborne illness, respectively, in the United States each year. The development of rapid, sensitive, and specific methods for detection of food-associated bacterial pathogens remains challenging.

Purpose: To develop a sensitive biosensing method for rapid detection of C. jejuni and Salmonella simultaneously in chicken and ground turkey wash solutions using magnetic nanobeads to separate and concentrate the target bacteria and quantum dots (QDs) as fluorescent markers.

Methods: Both streptavidin conjugated QDs 530 and QDs 620 were separately coated with the specific biotin conjugated anti-Salmonella and anti-C. jejuni antibodies. The magnetic nanobeads also were separately coated with the specific biotin conjugated anti-Salmonella and anti-C. jejuni antibodies. The conjugated magnetic nanobeads then were mixed with a sample containing Salmonella and C. jejuni. After immunomagnetic separation, the magnetic nanobeads-Salmonella and nanobeads-Campylobacter conjugates were mixed with the conjugated QDs 530 and QDs 620 in the same test tube. Unattached conjugated QDs were removed using immunomagnetic separation. Fluorescence spectrometer at 530 and 620 nm was used to measure the complexes of magnetic beads–S. Enteritidis-QDs and beads-C. jejuni-QDs with a total detection time of less than 2 hrs.

Results: C. jejuni (QDs 620) and S. Enteritidis (QDs 530), in pure culture, chicken carcass and ground turkey wash solutions were simultaneously separated and detected. The fluorescence intensities increased significantly with the increasing cell number of both bacteria. The multiple detection limit was 20-50 CFU/ml and the detection time was less than 2 hrs. 

Significance: This study would provide the poultry industry a more efficient rapid method for detection of major foodborne pathogens on products to ensure food safety.