Most of leafy vegetables used for fresh-cut industry are grown in soil and bacteria contamination from Escherichia coli O157 and Listeria monocytogenes can easily occur.Washing practices during minimal processing are able to reduce the bacterial load and allow to preserve the fresh-cut leafy vegetables for 5-7 days, of which 2 days of processing and 5 days of shelf-life. But the official standard procedures for the detection of bacterial pathogens require 4-5 days, thus faster and reliable methods are required to detect the pathogen presence without losing days of commercialisation.
In the framework of the EU project QUAFETY – Comprehensive approach to Enhance Quality and Safety of Ready to Eat Fresh products, scientists at University of Milano (Italy) and at University of Athens (Greece) have validated the technical efficiency of innovative diagnostic methods for the detection and quantification of Listeria monocytogenes and Escherichia coli O157:H7 in fresh-cut fruit and vegetables. Moreover, they have evaluated the efficacy and the viability for routine analysis of this diagnostic methods.For the work, the scientists developed different methods based on ELISA approach and compared these innovative methods with the standard official ISO procedures.
Results demonstrated the technical efficiency of the developed ELISA-based methods. All methods compared had similar sensitivity, specificity, negative predictive values and negative likelihood ratios. False positive results from ELISA method resulted in the reduction of positive predictive values. The efficacy and the viability for routine analysis of ELISA-based methods depend mostly on available equipment and technical expertise.
Source: Cavaiuolo M., Ferrante A., Paramithiotis S., Hadjilouka A., Tzamalis P., Drosinos E.H., ‘Validation of ELISA-based detection of L. monocytogenes and E. coli O157:H7 in fresh cut vegetables’, July-October 2014, Journal of Food, Agriculture & Environment, Vol. 12 (3&4), page 98-99.