9/18/2016 MPN Index Enrichment Techniques 100ml Lower Upper Zero tolerance or 0 cells per 25 grams of sample is 225734 517 required for food safety against Salmonella, Listeria,and Escherichia coli0157:H7 Must be able to find one or more cells among millons of other bacteria 350050504 91001000 10 How? -Pre-enrichment using non-selective media Use selective media to isolate the pathogen 060000 Confirm identity via biochemical tests and/or genetic authentification Preenrichment allows the bacteria to repair, recover and regain resistance to selective agents. Physiological States of Bacteria Traditional flowchart for isolation of Salmonella Outside of the lab,bacterial communities are species from foods highly dynamic Each community may involve the following physiological states /↓ 1.Injured and unable to grow on selective W书限K media 2.Viable but non-culturable 3.Biofilm-structured communities 4.Coordination of activities as a population via cell-cell communication 9/18/2016 6 21 Enrichment Techniques • Zero tolerance or 0 cells per 25 grams of sample is required for food safety against Salmonella, Listeria, and Escherichia coli O157:H7 • Must be able to find one or more cells among millons of other bacteria • How? - Pre-enrichment using non-selective media - Use selective media to isolate the pathogen - Confirm identity via biochemical tests and/or genetic authentification • Preenrichment allows the bacteria to repair, recover and regain resistance to selective agents. 22 Traditional flowchart for isolation of Salmonella species from foods 23 Physiological States of Bacteria • Outside of the lab, bacterial communities are highly dynamic • Each community may involve the following physiological states 1. Injured and unable to grow on selective media 2. Viable but non-culturable 3. Biofilm – structured communities 4. Coordination of activities as a population via cell-cell communication 24