Pulsed-field gel electrophoresis of Listeria monocytogenes strains: the PulseNet Europe Feasibility Study.

A feasibility study on standardized subtyping of Listeria monocytogenes by pulsed-field gel electrophoresis (PFGE) was performed in 2003 in Europe. The aim of the project was to identify veterinary, food, and public health reference laboratories that were willing to participate in the molecular surveillance of Listeria infections in Europe, as is done with PulseNet USA, and to test if the participants could generate results that were comparable with each other. A panel of strains and the methodology were sent to European laboratories, and images of PFGE gels were transferred electronically, then analyzed visually and with image analysis software. Only nine out of 43 gels were not fully satisfactory at the visual evaluation step stage. Computerized analysis showed that only three out of 33 gels gave dendrograms totally different from the reference dendrograms. Thus, the objectives of the study were met: most human and food European laboratories concerned with typing L. monocytogenes participated, images were transmitted electronically, and the overall quality of the gels was good.