Isolation and characterization of Shiga toxin-producing Escherichia coli from precooked sausages (morcillas)

The aim of the study was to establish the microbiological quality of morcillas, typical Argentine sausages, and to investigate the presence of Shiga toxin-producing Escherichia coli (STEC). Between October 2001 and October 2002, a total of 100 morcilla samples were analysed. Several samples showed high levels of total aerobic mesophilic bacteria counts, molds and yeasts. The samples analysed contained Enterobacteriaceae (100%) and fecal coliforms (81%), indicating inadequate application of the thermal treatment and deficient hygiene conditions during the elaboration of the product. STEC strains were isolated from three out of 100 (3%) morcilla samples. Two strains (2%) were characterized as E. coli O157:H7 stx2+stx2vh-a/eae/EHEC-hlyA and one strain (1%), as E. coli O26:H11 stx1/eae/EHEC-hlyA. Considering both the high microbial count in all tested samples and the presence of STEC strains in three of them, morcillas should be considered a food unsafe to consume when inadequately cooked.