Abstract
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.
Highlights
In the meat industry, the significance of enterohemorrhagic Escherichia coli (EHEC) as a serious public health problem is undoubtedly recognised
E. coli O157:H7 CM454 were placed in physiological conditions where they exhibited differential attachment features, namely the induction of specific and non-specific adhesion to the extracellular matrix (ECM) when grown in LB and DMEM, respectively (Chagnot et al, 2013a)
In LB, the surface of the muscles was covered unevenly by E. coli O157:H7 CM454, which appeared to adhere to specific structures of the epimysium by following the outline of the muscle fibres, which was especially apparent over the extensor digitorum longus (EDL) (Figure 1A)
Summary
The significance of enterohemorrhagic Escherichia coli (EHEC) as a serious public health problem is undoubtedly recognised. Foodborne illness associated with the consumption of meat. Colonisation of Meat Tissue by E. coli O157:H7 products contaminated by EHEC has been reported and E. coli O157:H7 is the most frequently associated serotype. While the muscle masses of healthy animals are sterile (Gill, 1979), bacterial contamination of meat can occur at slaughtering, mainly upon transfer to carcasses at the dehiding stage and even when good practices are strictly respected, i.e. excluding evisceration accident (Giaouris et al, 2014). The respect of good hygienic practices in the beef industry during slaughtering reduces contamination of carcasses, but cannot guarantee the absence of E. coli O157:H7 from meat (Rhoades et al, 2009). The survival of bacteria in meat could depend upon their ability to adhere to meat surfaces
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