Colonisation of meat by escherichia coli O157:H7: Investigating bacterial tropism with respect to the different types of skeletal mMuscles, Subtypes of mMyofibres, and postmortem time

Caroline Chagnot (1, 2) , Annie Venien (2) , Sandra Renier (1) , Nelly Caccia (1) , Régine Talon (1) , Thierry Astruc (2) , Mickaël Desvaux (1)

1 MEDIS - Microbiologie Environnement Digestif Santé
2 QuaPA - Qualité des Produits Animaux

Escherichia coli O157:H7 is an enterohaemorrhagic E. coli (EHEC) responsible for serious diseases, especially pediatric, and of great concern for the meat industry. Meat contamination by EHEC occurs at slaughtering, especially at dehiding stage, where bacteria can be transferred from hides to carcasses. The skeletal muscle tissues comprise four major types of myofibres, which differ in their contraction velocity and metabolism. Myofibres are surrounded by the extracellular matrix (ECM). Adhesion of E. coli O157:H7 to meat was investigated considering well-defined types of skeletal muscle and their constituent myofibres as well as postmortem changes in muscle, using fluorescence microscopy and immunohistochemical analyses. By analysing the adhesion of E. coli O157:H7 to model oxidative (soleus) and glycolytic [extensor digitorum longus (EDL)] skeletal muscles, it first appeared that differential adhesion occurred at the surface of these extreme skeletal muscle types. At a cellular level, bacterial adhesion appeared to occur essentially at the ECM. Considering the different constituent myofibres of types I, IIA, IIX and IIB, no significant differences were observed for adhering bacteria. However, bacterial adhesion to the ECM was significantly influenced by postmortem structural modifications of muscle tissues. By providing information on spatial localisation of E. coli O157:H7 on meat, this investigation clearly demonstrated their ability to adhere to skeletal muscle, especially at the ECM, which consequently resulted in their heterogeneous distribution in meat. As discussed, these new findings should help in reassessing and mitigating the risk of contamination of meat, the food chain and ultimately human infection by EHEC.

Mots clés: voluntary muscle; extracellular matrix; meat product; food contamination; bacterial adhesion; foodborne pathogen; pathogen

Mots clés: escherichia coli; muscle squelettique; agent pathogène; adhésion bactérienne; matrice extracellulaire; contamination alimentaire

Domaines: Microbiologie et Parasitologie

Caroline Chagnot, Annie Venien, Sandra Renier, Nelly Caccia, Régine Talon, et al.. Colonisation of meat by escherichia coli O157:H7: Investigating bacterial tropism with respect to the different types of skeletal mMuscles, Subtypes of mMyofibres, and postmortem time. Frontiers in Microbiology, 2017, 8, pp.1366. ⟨10.3389/fmicb.2017.01366⟩. ⟨hal-01581624⟩