A high efficiency pre-treatment method for elution of pathogenic bacteria in lettuces

Abstract

Many current studies on rapid detections of pathogenic bacteria in foods focused on the construction of detection methods, neglecting pre-treatment. In fact, it is also a key step to efficiently elute pathogenic bacteria from food samples for rapid detections, and even, it can determine the success or failure of an assay. In this study, we used Escherichia coli, Salmonella enteritidis and Listeria monocytogenes as model bacteria to compare elution efficiency of different eluants, explore the effect of surfactant, ionic strength, protein (or amino acid and peptide), and enzyme on the recovery rate of bacteria in lettuces, and compare the compound effect caused by multiple of factors. Finally, we developed an efficient bacterial recovery method and confirmed the superiority of this method to analyze the bacterial diversity of the eluants from lettuces. The results showed that the recovery efficiency of Escherichia coli, Salmonella enteritidis and Listeria monocytogenes, which were artificially contaminated with approximately 10 5 CFU/g in lettuces, could reach 94.4%, 90.6% and 93.7% by using 10 mM Tris·HCl (pH 9.5) with 0.1% peptone and 300 U/100 mL of cellulase, and furthermore, the elution efficiency could reach 99.6%, 98.6% and 100% under the aid of a 2 min stomaching. For the lettuce samples only with native bacteria, the recovery rate reached 92.1% for viable aerobic bacteria by this method, being approximately 10% higher than the modified previous method. The bacterial diversity of the eluted solution was analyzed, and the result was significantly improved. Considering these advantages, it is important to improve the elution efficiency to achieve rapid and accurate detection of pathogenic bacteria in lettuces.