Molecular typing of Listeria monocytogenes strains isolated from food, feed and animals: state of play and standard operating procedures for pulsed field gel electrophoresis (PFGE) typing, profile interpretation and curation

EFSA has contracted ANSES (Food Safety Laboratory, Maisons-Alfort, France) to provide assistance related to establishing molecular typing data collection for Listeria monocytogenes from food, feed and animals.This document is the final report scheduled in the contract; it comprises three parts.The first part contains a comparison and evaluation of different methods for molecular testing of Listeria monocytogenes isolates for outbreak detection and epidemiological surveillance: fluorescence amplified fragment length polymorphism, multiple-locus variable-number tandem-repeat analysis, repetitive-sequence-based polymerase chain reaction, multi locus sequence typing, and whole genome sequencing.The performances of each of these methods are assessed in comparison to the current reference method, pulsed-field gel electrophoresis, their advantages and drawbacks are discussed.The second part presents an enquiry to the National Reference Laboratories for Listeria monocytogenes to make an inventory of available data and typing methods used.We have drafted and dispatched this questionnaire as European Union Reference Laboratory for Listeria monocytogenes.It contains 3 parts: i) importance of strain collections, type of data and storage available in the National Reference Laboratories, (ii) more detailed information on potential molecular typing data available at national level and diversity of molecular typing methods used, (ii) methods scheduled to be implemented at short term.All replies from 35 National Reference Laboratories are provided in this report.The third part of the report contains a comparison of existing Standard Operating Procedures for pulsed-field gel electrophoresis testing of Listeria monocytogenes strains, for acquisition and quality assessment of images and for curation.It also proposes one Standard Operating Procedure for each topic.