Rapid Identification of Three Foodborne Pathogens in Ready-to-Eat Bulk Foods by Matrix-Assisted Laser Desorption Ionization-Time of Flight Mass Spectrometry
Rapid Identification of Three Foodborne Pathogens in Ready-to-Eat Bulk Foods by Matrix-Assisted Laser Desorption Ionization-Time of Flight Mass Spectrometry
The matrix-assisted laser desorption ionization-time of flight mass spectrometry(MALDI-TOF MS)diagnostic tool was used to rapidly detect and identify three foodborne pathogens,Salmonella,Staphylococcus aureus and Bacillus cereus in ready-to-eat bulk foods in this study.The best method was identified by optimizing and screening various experimental conditions such as spot sampling method,pre-treatment method,different media and culture time,and its detection limit and stability were evaluated.Meanwhile,the established method was compared with multiplex PCR and the other biochemical identification methods such as VITEK 2 to contrast the consistency of the three identification results.Finally,batch food sample testing was carried out to explore the applicability of using MALDI-TOF MS to test ready-to-eat bulk foods.Results indicated that all the identification scores of the three bacteria were higher than 95%for the same batch and different passages,with a coefficient of variation of less than 2%.It demonstrated that the established method had good repeatability and stability,and the detection limit was 105 CFU/mL.The results of strain identification by MALDI-TOF MS were highly consistent with those of multiplex PCR and biochemical identification methods.Moreover,the MALDI-TOF MS method was more specific and efficient.Regarding spot sampling,the three covering methods showed higher average identification scores than the sandwich and mixed methods,all of which scored 99.9%.The 1 μL+1 μL covering method spot sampling approach obtained higher average peak numbers,and more complex and stronger characteristic peaks.Regarding pre-treatment,the formic-acid-acetonitrile method obtained a higher peak volume and peak intensity than other bacterial treatment methods,with an average identification score of 98%or higher.At the same time,the matching degree with the database spectrum was higher.In summary,MALDI-TOF MS method was not only sensitive,specific,accurate and rapid in foodborn pathogen identification,but also had simple operation and intuitive in results.As a powerful supplement to the national standard method,it provided a viable alternative for analysing,identifying and typing foodborne
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