Seven housekeeping

genes (acbZ, bglA, cat, dapE, dat, ldh, and lhkA) were selected for the MLST analyses (Additional file 2: CAL-101 mw Table S2) [9]. Alleles and sequence types (ST) are freely I-BET-762 nmr available at http://​www.​pasteur.​fr/​mlst. For analyses, sequences were concatenated either for the virulence or the housekeeping genes in an MLST scheme. For each MLST locus, including the 748 L. monocytogenes strains, an allele number was given to each distinct sequence variant. MLST analysis links profiles so that the sum of the distances (number of distinct alleles between two profiles) is minimized [24]. Each circle represented in Figure 3 corresponds to a ST number, attributed to each distinct combination of alleles on the seven genes. The size of the circle corresponds to the number of strains with that particular profile. The dendrograms of the concatenated nucleotide sequences of virulence and housekeeping genes AMN-107 manufacturer with the

Neighbor-Joining (NJ) method and MLST analysis were performed using BioNumerics v4.6. Optical mapping Optical maps were prepared on the Argus™ Optical Mapping System by OpGen (Gaithersburg, MD USA), as described previously [25]. This method scans and assesses the architecture of complete bacterial genomes. Briefly, following cell lysis, genomic DNA molecules were spread and immobilized onto derivatized glass slides and digested by NcoI. After restriction digestion, a small gap in the DNA at the precise location of the restriction endonuclease cleavage site is left. The DNA digests were stained with YOYO-1 fluorescent dye, and photographed with a fluorescence microscope interfaced with a digital camera. Automated image-analysis software located and sized fragments, based on YOYO-1 binding and assembled multiple scans, into whole-chromosome optical maps. The average size of each restriction fragment (measured in 30–100 different molecules in the assembly) was determined and used to create a linear “consensus 4-Aminobutyrate aminotransferase map” on which each restriction

site is represented by a vertical line. Nucleotide sequences The DNA sequences of the MLST loci have been deposited in GenBank under accession numbers EU294615-EU294706 (abcZ), EU294707-EU294797 (bglA), EU294798-EU294889 (cat), EU294890-EU294981 (dapE), EU294982-EU295073 (dat), (EU295074-EU295165 (ldh), EU295166-EU295257 (lhkA), EU294523-EU294614 (prfA), EU295258-EU295336 (actA), and EU295337-EU295423 (inlA). Acknowledgements This study was supported by grants from the Conseil Régional du Centre and the Ministère de l’Agriculture et de la Forêt, by Institut Pasteur (Paris, France), and the Institut de Veille Sanitaire (Saint-Maurice, France). It was also funded by an INRA food research programme. S. Témoin holds a Doctoral fellowship from the Région Centre and the Institut National de Recherche Agronomique.