1/21/20091Microorganisms Causing Foodborne DiseaseMicroorganisms Causing Foodborne Diseaseoodbo aoodbo aEnterobacteriaceaeFamilyGenus SalmonellaEnterobacteriaceaeFamilyGenus SalmonellaFamilyEnterobacteriaceaeFamilyEnterobacteriaceae•Gram-negative• Non-sporeforming rods•Faculatively anaerobic•Gram-negative• Non-sporeforming rods•Faculatively anaerobic•Faculatively anaerobic• Oxidase negative• Glucose fermentative• Generally motile•Faculatively anaerobic• Oxidase negative• Glucose fermentative• Generally motilePeritrichous flagella1/21/20092SalmonellaSalmonella• Named after Dr. D. E. Salmon– First described Salmonella cholerae-suis• Currently only 2 species are recognized–S. bongori–Senterica• Named after Dr. D. E. Salmon– First described Salmonella cholerae-suis• Currently only 2 species are recognized–S. bongori–SentericaS. enterica• 6 subspecies»enterica»salamae»arizonae»diarizonae»houtenae»IndicaS. enterica• 6 subspecies»enterica»salamae»arizonae»diarizonae»houtenae»IndicaPrincipal biochemical characteristicsPrincipal biochemical characteristics• Lactose negative• Lysine decarboxylase positive•H2S positive•Urease negative• Lactose negative• Lysine decarboxylase positive•H2S positive•Urease negative•Urease negative•Urease negative• 0.8% of strains can ferment lactose• A few strains do not produce H2S• 0.8% of strains can ferment lactose• A few strains do not produce H2SSalmonellaSalmonella• Salmonellae are separated in somatic groups (O antigens) and flagellar types (H antigens)• About 2,400 serovars (or serotypes) have been described• Salmonellae are separated in somatic groups (O antigens) and flagellar types (H antigens)• About 2,400 serovars (or serotypes) have been describedhave been described• Example of correct nomenclature:–Salmonella entericasubsp. entericaserovar Typhimurium– Abbreviated: SalmonellaTyphimurium• After having defined by full name• Also there is a phage-based classification– Phage typeshave been described• Example of correct nomenclature:–Salmonella entericasubsp. entericaserovar Typhimurium– Abbreviated: SalmonellaTyphimurium• After having defined by full name• Also there is a phage-based classification– Phage types1/21/20093Growth characteristicsGrowth characteristics• Temperature– Minimum 7°C– Maximum 47°C– Optimum 37°C•pH• Temperature– Minimum 7°C– Maximum 47°C– Optimum 37°C•pHp– Minimum• Acetic acid 4.7• HCl 4.05–Optimum 7.0•aw – Minimum0.93p– Minimum• Acetic acid 4.7• HCl 4.05–Optimum 7.0•aw – Minimum0.93Heat resistanceHeat resistance• Non-thermoduric•S.Senftenberg 775W is heat resistant–D71in milk = 0.09 minDfST hi i i ilk 0 003 i• Non-thermoduric•S.Senftenberg 775W is heat resistant–D71in milk = 0.09 minDfST hi i i ilk 0 003 i–D71for S.Typhimurium in milk = 0.003 min• Heating mestruum affects heat resistance–D70for S.Typhimurium in chocolate sauce = 11.3 – 17.5 h.–D71for S.Typhimurium in milk = 0.003 min• Heating mestruum affects heat resistance–D70for S.Typhimurium in chocolate sauce = 11.3 – 17.5 h.EcologyEcology• Most salmonellae infect a wide range of animal species• Some serovars are host adapted• Most salmonellae infect a wide range of animal species• Some serovars are host adapted–S.Enteritidis PT4, S.Pullorum, S.Gallinarum in poultry –S. Cholerae-suis in pigs–S. Tiphy in humans–S.Enteritidis PT4, S.Pullorum, S.Gallinarum in poultry –S. Cholerae-suis in pigs–S. Tiphy in humans1/21/20094Clinical featuresClinical features• Enteritis–Diarrhea, nausea and fever• Incubation period• Enteritis–Diarrhea, nausea and fever• Incubation periodp–6 – 48 h• Infectious dose–1 to 106cellsp–6 – 48 h• Infectious dose–1 to 106cellsPathogenesisPathogenesis• Pathogenesis– Adhesion to epithelial cells of the ileum via mannose-resistant fimbriae– Bacterial uptake by host cells (endocytes)• Pathogenesis– Adhesion to epithelial cells of the ileum via mannose-resistant fimbriae– Bacterial uptake by host cells (endocytes)–Passage through epithelial cells within a vacuole, where the bacterium multiplies– Influx of inflammatory cells leading to the release of prostaglandins– Prostaglandins activate adenylate cyclase which produces fluid secretion to the intestinal lumen–Passage through epithelial cells within a vacuole, where the bacterium multiplies– Influx of inflammatory cells leading to the release of prostaglandins– Prostaglandins activate adenylate cyclase which produces fluid secretion to the intestinal lumenActivity in foodsActivity in foods•Low awenhances the survival of Salmonella–The lower the awthe greater the survival rate•Low awenhances the survival of Salmonella–The lower the awthe greater the survival rateSurvival of Salmonella in meringue powder as affected by aw050100150200250Days of storage0.3 0.2 0.1aw1/21/20095Survival of Salmonellain different foodsSurvival of Salmonellain different foodsCommodityCommodity TemperatureTemperature Survival timeSurvival timeButterButter --23 to 2523 to 25°°CC >10 weeks>10 weeksRoom tempRoom tempMilkMilkRoom temp.Room temp.6 months6 monthsIce boxIce boxVarious vegetablesVarious vegetables 2 to 42 to 4°°CC >28 days>28 daysChocolateChocolate Room temp.Room temp. MonthsMonthsFoods associated with SalmonellainfectionFoods associated with Salmonellainfection• Eggs –Salmonellaserovar Enteritidis•Meat• Eggs –Salmonellaserovar Enteritidis•Meat• Cheese–S.Zanzibar•Chocolate• Cheese–S.Zanzibar•Chocolate•Meat–S.Typhimurium • Fruits and vegetables–S.Montevideo (tomatoes)–S.Poona (cantaloupes) –S.Newport (mangoes)•Meat–S.Typhimurium • Fruits and vegetables–S.Montevideo (tomatoes)–S.Poona (cantaloupes) –S.Newport (mangoes)Chocolate–S.Eastbourne• Milk–S.Typhimurium–S.NewbrunswickChocolate–S.Eastbourne• Milk–S.Typhimurium–S.NewbrunswickTransmission routesTransmission routes1/21/20096S.EnteritidisS.Enteritidis• Associated with eggs• Present in the yolk at oviposition• Food associated:– Homemade mayonnaise w/raw eggs–Tartar sauceEgg nogg• Associated with eggs• Present in the yolk at oviposition• Food associated:– Homemade mayonnaise w/raw eggs–Tartar sauceEgg nogg–Egg nogg– Milk shakes– Mousse– Ice cream• Control–Decreasing S.Enteritidis populations at the