Combination of filtration and immunomagnetic separation based on real-time PCR to detect foodborne pathogens in fresh-cut apple

Abstract

Rapid detection methods require pre-enrichment culture in order to detect low levels of foodborne pathogens. To rapidly detect foodborne pathogens, enrichment culture processes could be replaced. Filtration and immunomagnetic separation methods have been identified to effectively concentrate and separate target pathogens from foods. In this study, a combination of filtration and immunomagnetic separation (IMS) has enabled the rapid and sensitive detection of foodborne pathogens. The pretreatment method, including separation and concentration procedures, increased sensitivity 10–100-fold. The sensitivity of a combination method using filtration and IMS to detect Escherichia coli O157:H7 and Salmonella enterica subsp. enterica serovar Typhimurium was 100–101 CFU/10 mL. In fresh-cut apples, IMS combined with filtration effectively improved the detection limit of real-time PCR to 2.70 × 101 CFU/g in E. coli O157:H7 and 1.80 × 102 CFU/g in Salmonella. The filtration simplified processing of large-volumes (250 mL) and effectively concentrated pathogens while decreasing immunomagnetic beads used in IMS. Bacterial concentration by IMS combined with filtration increased sensitivity 10–100-fold compared with control. In addition, the application of IMS effectively removed concentrated residual food material (10–15 mg/mL) after filtration, improving relative sensitivity. In conclusion, this method may detect foodborne pathogen in foods such as fresh-cut fruits in a more rapid and sensitive fashion than traditional culture-based methods.