A rapid method for the detection of foodborne pathogens by extraction of a trace amount of DNA from raw milk based on amino-modified silica-coated magnetic nanoparticles and polymerase chain reaction

• We found ASMNPs can adsorb a trace amount of DNA of pathogens from milk extracts.
• Pathogen can be detected sensitively and rapidly using this magnetic probe and PCR.
• Multiple pathogens can be detected only using this simple probe to capture all DNA.

A method based on amino-modified silica-coated magnetic nanoparticles (ASMNPs) and polymerase chain reaction (PCR) was developed to rapidly and sensitively detect foodborne pathogens in raw milk. After optimizing parameters such as pH, temperature, and time, a trace amount of genomic DNA of pathogens could be extracted directly from complex matrices such as raw milk using ASMNPs. The magnetically separated complexes of genomic DNA and ASMNPs were directly subjected to single PCR (S-PCR) or multiplex PCR (M-PCR) to detect single or multiple pathogens from raw milk samples. Salmonella Enteritidis (Gram-negative) and Listeria monocytogenes (Gram-positive) were used as model organisms to artificially contaminate raw milk samples. After magnetic separation and S-PCR, the detection sensitivities were 8 CFU mL−1 and 13 CFU mL−1 respectively for these two types of pathogens. Furthermore, this method was successfully used to detect multiple pathogens (S. Enteritidis and L. monocytogenes) from artificially contaminated raw milk using M-PCR at sensitivities of 15 CFU mL−1 and 25 CFU mL−1, respectively. This method has great potential to rapidly and sensitively detect pathogens in raw milk or other complex food matrices.

AFM images showed ASMNPs could directly adsorb a trace amount of genomic DNA of pathogens without further conjugating with biological molecules even in complex matrices. (a. ASMNPs; b. Complexes of ASMNPs and purified genomic DNA of S. Enteritidis; c. Complexes of ASMNPs and extraction of artificial contaminated raw milk).Figure optionsDownload as PowerPoint slide