Reproducibility and discriminatory power of the subtyping methods Table 1 shows the subtyping results of isolates used to evaluate the reproducibility, the discriminatory power and the ability to recognize same-type groups of isolates using PFGE and fAFLP. Isolates included in the study as duplicates gave indistinguishable fAFLP types and PFGE types (Table 1). Table 1 also shows that distinct PFGE types and fAFLP types

were observed in each groups of isolates associated find more with outbreak or sporadic cases, except for TS isolates group 03: PFGE type 120/191 was detected in L. monocytogenes TS67, TS56 (duplicate of TS77) and TS 39, but displayed two different fAFLP types i.e. VII.27 and VII.27a. These 2 fAFLP types were indistinguishable except

for a small additional ‘shoulder’ after a double peak of 206 base pairs, as seen on the PeakScanner scan, present in strains TS39 and TS67 (type VIIa.27a) but not in isolate TS56 (type VIIa.27). To rule out any fluorescent artefacts, the 3 isolates were processed in triplicate on separate occasions and the fAFLP profile obtained by each replicate was always the same, including the ‘shoulder’ at 206 bp with strains TS39 and TS67. Both subtyping methods separated the isolates into three distinct BAY 63-2521 solubility dmso groups correlating with L. monocytogenes genetic lineages I, II and III (Figure 1; Figure 2; Figure 3). The 11 reference strains, including the 8 CLIP and the 3 fully sequenced strains, were classified by both fAFLP and PFGE, into the expected genetic lineages (Figure 1; Figure 2; Dichloromethane dehalogenase Figure 3). The discriminatory power of fAFLP and PFGE was evaluated using 97 isolates including field strains, references strains, sporadic cases and representative isolates from each outbreak. The ID calculated from the typing results of fAFLP and PFGE is shown in Table 3. The ID calculated from fAFLP typing was 0.993 and from PFGE typing 0.996. Both typing techniques were found to be more discriminatory for L. monocytogenes Lineage II than for those of lineage I. Figure 2 Dendogram

of similarity for 86 L. monocytogenes isolates based on Apa I-PFGE type using the Dice coefficient and UPGMA. Figure 3 Dendogram of similarity for 86 L. monocytogenes isolates based on Asc I-PFGE type using the Dice coefficient and UPGMA. H: human, F: food ; E: environment ; A: animal. Table 3 PFGE and fAFLP typing results from a panel of 97 L. monocytogenes isolates with index of discrimination (ID) L. monocytogeneslineages Serogroups1or serotype2 Number of isolates Number of PFGE3types PFGE ID4 Number of fAFLP3types fAFLP ID4 I IVb 35 36 0.988 33 0.981 IIb 11 II IIa 45 45 0.995 43 0.989 IIc 5 III 4a 1 1 n/a 1 n/a Total: 97 82 0.996 76 0.993 1 Serogrouping performed by multiplex PCR [4]: results are from both the European Reference Laboratory (EURL) for L. monocytogenes and the UK National Reference laboratory (UK-NRL) for Listeria. 2 Based on sero-agglutination performed by EURL.