Evaluation of ISO enrichment real-time PCR methods with internal amplification control for detection of Listeria monocytogenes and Salmonella enterica in fresh fruit and vegetables.

ABSTRACT

AIMS: To provide with a quick method for qualitative detection, in less than three days, of Salmonella enterica and Listeria monocytogenes in fresh fruit and vegetables. METHODS AND RESULTS: The method was based on coupling International Standard Organization (ISO) enrichment to a real-time PCR with internal amplification control (IAC), in a duplex format, without additional DNA purification. The performance was tested on different plant products. Both bacterial pathogens were consistently detected with a limit of detection (LOD) of 1 CFU in 25 g after enrichment, except for soybean sprouts. Levels of S. enterica, ranging from 1 to 10 CFU in 25 g after enrichment were detected with different enrichment broths. CONCLUSIONS: For both pathogens, the LOD was similar to that of the corresponding ISO method, while decreasing the analysis time and handling needs. SIGNIFICANCE AND IMPACT OF THE STUDY The agreement between standard ISO and the enrichment real-time PCR(IAC)-based methods make the latter method as a promising alternative for quick and reliable detection of food-borne pathogens in fresh fruit and vegetables in routine laboratories.