Study on a Pre-enrichment Medium for the Simultaneous Recovery of Salmonella spp.，Escherichia coli and Staphylococcus aureus

Abstract:

This text involved with a pre-enrichment medium for the simultaneous recovery of Salmonella spp.，Escherichia coli and Staphylococcus aureus.This medium is named buffered saline broth(BSB)，which contains peptone 10g，beef exact 3g，disodium hydrogen phosphate 9g，potassium dihydrogen phosphate 1.5g，additive 50g，deionized water 1 000mL，pH7.2.1cfu per one milliliter of Salmonella spp.，Escherichia coli and Staphylococcus aureus in saline were stimutaneously added to 97 mL of BSB，buffered peptone water，lactose broth，nutrient broth，Escherichia coli broth，rappaport-vassiliadis enrichment broth，7.5% sodium chloride enrichment medium，respectively，and incubated for 18h at 37℃.The results showed BSB was the best enrichment medium，in which Salmonella spp.，Escherichia coli and Staphylococcus aureus multiplied at nearly same speed，and reached at 106、106、107cfu/mL，respectively.Multiplex PCR produced specific amplicons of expected sizes，284bp for Salmonella spp.invA gene，622bp for Escherichia coli phoA gene，484bp for Staphylococcus aureus nuc gene.In contrast，the three bacteria couldnt multiply harmoniously in the other six media.So BSB might be considered as the medium，which could enrich above mentioned three bacteria.

Key words:Salmonella spp.，Escherichia coli，Staphylococcus aureus，Enrichment medium，Multiplex PCR