Persistence and reduction of Shiga toxin-producing Escherichia coli serotype O26:H11 in different types of raw fermented sausages.

Fermented sausages have been identified as source of several outbreaks of Shiga toxin-producing Escherichia coli (STEC). Illnesses linked to non-O157 STEC serotypes appear to be on the rise worldwide, and serogroup O26 is the second most reported in Europe after O157. However, data on the behavior of serogroup O26 in food are rare, so that the aim of this study was to investigate the survival of STEC O26:H11 in different types of fermented sausages ("Teewurst", fast-ripened and long-fermented salami). Challenge studies were performed with an inoculation cocktail which consisted of three STEC O26:H11 strains isolated from human, cattle and food sources. In the short-ripened spreadable sausage type "Teewurst" STEC counts decreased by only 0.5 log within 28days. In contrast, STEC reductions from 2.2 to 2.6 log units were observed in the different salami products, while the most pronounced decrease of 1.0 log unit within one day was detected in fast-ripened sausages with glucono delta-lactone (GdL). Moreover, numbers of the food-associated E. coli O26:H11 strain were significantly higher (p<0.001) than those of the human and cattle STEC O26:H11 strains in all types of fermented sausages. Approximately 60% of all STEC isolates from GdL salami shared the genotypic virulence profile of the food-associated E. coli O26:H11 strain. In summary, hurdles of acidification and drying during salami ripening resulted in reductions of STEC O26:H11 counts. However, our results also indicate that STEC O26:H11 can persist in the environment of "Teewurst" and might therefore pose a risk to public health.