Molecular Analysis

M13 sequence-based polymerase chain reaction (M13-PCR), derived from a RAPD technique, allows differentiating between various strain patterns. M13 typing was performed as described (Glasset et al., 2016). The DNA profiles were analyzed with BioNumerics 7.1 software (Applied Maths). The software compared the DNA profiles and clustered the strains according to their similarity.

The toxin gene profiles were identified by assessing the presence of the cytK-1, cytK-2, HBLA, HBLC, HBLD, NHEA, NHEB, NHEC, hlyII and ces genes by PCR using specific primers (Glasset et al., 2016). The strains were then clustered into genetic signatures (GS) according to their different combinations of presence/absence patterns (Glasset et al., 2021).

The strains were affiliated to one of the seven known phylogenetic groups according to the partial sequencing of the panC gene (Guinebretière et al., 2008). The production of the enterotoxins NHE and HBL was tested with the immunological tests BCET-RPLA Toxin Detection (Oxoïd) and Tecra (BDE VIA, 3M-Tecra) kits, respectively (Guinebretière et al., 2002).