The laboratory has been accredited by the French Accreditation Committee, COFRAC for this PFGE method as an internal method (Accreditation No. 1–2246, Section Laboratories, http://​www.​cofrac.​fr). Fragments obtained from the digestion by each of the enzymes

were separated by gel electrophoresis. Gels were stained with ethidium bromide and banding patterns visualized under UV light, using the Gel Doc Eq system and Quantity One software (Bio-Rad). DNA patterns generated were analyzed with BioNumerics software (V 6.1, Applied Maths, Kortrijk, Belgium). Algorithms available within the program were used to compare patterns. For each enzyme, dendrograms were produced, using the Dice coefficient and UPGMA, with a 1% tolerance Venetoclax limit and 1% optimization. The dendrogam settings were chosen according to the PulseNet AUY-922 cell line Europe recommendation [24]. Profiles were analyzed according to the standard operating procedure (SOP) developed at the EURL [15]. PFGE profiles were classified as different if there

was at least one band different between them. Each PFGE profile was arbitrarily assigned a number. Reproducibility of the subtyping methods Two strains were included blindly as duplicates cultures (Table 1). Discriminatory power of the subtyping methods The ability of the two subtyping methods to discriminate L. monocytogenes strains was assessed in two ways: (1) Determining the ability of the typing methods to recognize strains that are epidemiologically linked (Table 1).   (2) Determining the ability of the typing methods to discriminate unrelated strains by calculating the Simpson’s index of diversity (ID) [25]. The ID was calculated from PFGE and FAFP

results of 97 isolates comprising field strains (75 isolates), references strains (11 isolates), sporadic cases and one representative isolate from each of the outbreaks shown in Table 1 (11 isolates).   Results Molecular serogrouping Molecular serogrouping results from the 109 isolates were concordant between the two testing laboratories Sucrase and were as follows: 46 IIa strains; 12 IIb strains; 10 IIc strains; 40 IVb strains. One isolate did amplify in the multiplex PCR assay and was subsequently serotyped by conventional sero-agglutination by EURL as 4a strain. The 11 reference strains (8 CLIP and 3 fully sequenced strains) were found to belong to the expected serogroup (Table 2). In both laboratories, the same four serogroup IVb strains, displayed an unusual multiplex PCR profile to that usually observed with IVb strains, with an additional band due to the amplification of the lmo0737 gene fragment as previously described [26]. Subtyping data Each fAFLP and PFGE type contained isolates belonging to only one of the 4 molecular serogroups, or serotype 4a, except for one PFGE type (81/194) which contained isolates from serogroups IIa and IIc (Figure 1). Figure 1 Dendogram of similarity for 86 L.