Salmonella spp.
Salmonella spp. is found in the stools of infected individuals (human and animals), which can affect shellfish harvesting areas through faecal contamination of watercourses. Most salmonellae bacteria can cause food poisoning (gastroenteritis) in humans that consume contaminated shellfish, and the resulting illness can be more severe than that induced bynorovirus.
No single method has been found to be suitable for the detection of Salmonella spp. in all foods however ISO 6579 - Microbiology of food and animal feeding stuffs - Horizontal method for the detection of Salmonella spp. has been shown to be suitable for bivalve molluscs. ISO 6579 is stipulated in EU Regulations as the reference method for salmonellae for official control testing.
The method involves pre-enrichment in buffered 1% peptone water, followed by enrichment in Muller-Kauffmann tetrathionate broth containing novobiocin and Rappaport Vasiliadis soya peptone broth.
Presumptive salmonellae are identified on two selective agar media (xylose lysine desoxycholate agar and a medium of the laboratory's choice). Biochemical screening on triple-sugar iron agar, in conjunction with urease media, is then used. The presence ofSalmonella spp. is confirmed using biochemical and serological characterisation tests.
An end-product standard requiring the absence of Salmonella spp. in 25g of shellfish flesh is specified under Regulation (EC) No. 2073/2005 on the microbiological criteria for live bivalve shellfish as foodstuffs.
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