Detection of enteropathogenic Escherichia coli in spreadable dry sausage

Fresh Mettwurst (a dry sausage eaten relatively fresh) is normally made with the aid of starter cultures. 2.1% and 3.0% lactate was added to part of a batch of Mettwurst and the sausages were inoculated with different levels of various serovars of enterohaemorrhagic E. coli (EHEC). These were E. coli O157:H7, O157:H-, O111:H- and O26:H11 from the collection of the Robert Koch Institute in Berlin. The sausages were ripened for 2 days (at about 20 degrees C), then sored for 2 and 4 weeks at 4 degrees C and then examined. To check the ripeness and state of hygiene of the fresh Mettwurst the numbers of lactobacilli, micrococci, total bacterial count, Enterobacteriaceae and pseudomonads were determined. The pH and a(w) and also the D-lactic acid content were measured and colour and spreadability were also assessed. The indicator substrates Fluorocult (R) E. coli O157:H7-agar, MacConkey sorbite agar and the recently developed Enterohaemolysin agar with Vancomycin were used to detect and confirm EHEC. Further methods of enrichment or confirmation of EHEC were immuno-magnetic separation (IMS, up to now only for E. coli O157), slide agglutination and toxin determination (for Shiga-like toxins). In spite of dry sausage ripening being typical it was found that the EHEC survived ripening and storage but did not increase in numbers. The result was the same for all Mettwurst, irrespective of the EHEC serovars with which the sausage was inoculated and irrespective of whether lactate was added or not. Even the level of organisms inoculated (between 1000 org./g and 2 org./g) had no decisive influence on the result. EHEC-contaminated fresh Mettwurst can therefore be a potential risk of infection to the consumer. Manufacturers must therefore strictly observe the hygiene regulations in relation to GMP and HACCP.