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. © 2009 The Society for Applied Microbiology.