Characterization of Extended Spectrum Cephalosporin-Resistant <i>Escherichia coli</i> Strains Isolated from Raw Poultry Carcasses in Catering Services in Northern Greece oleh Vangelis Economou, Georgios Delis, Dimitra Stavrou, Panagiota Gousia, Anestis Tsitsos, Tilemachos Mantzios, Eirini Chouliara, Nikolaos Kolovos, Nikolaos Soultos