1 Microorganisms Causing Foodborne Disease Family Enterobacteriaceae Shigella andYersinia enterocolitica Shigella ã 4 serogroups and species –S. dysenteriae (serogroup A) –S. flexnerii (serogroup B) –S. boydii (serogroup C) –S. sonnei (serogroup D) Shigella ã Characteristics of the microorganism ã Non-motile ã Does not ferment lactose ã Gas is not produced from glucose fermentation ã IMViC is -+-- ã Does not produce lysine decarboxylase ã H 2 S and urease negative 2 Shigella ã Similar resista
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  Microorganisms Causing Foodborne Disease Family Enterobacteriaceae Shigella  and Yersiniaenterocolitica  Shigella  ã4 serogroupsand species  – S. dysenteriae  (serogroupA) – S. flexnerii  (serogroupB) – S. boydii  (serogroupC) – S. sonnei  (serogroupD) Shigella  ãCharacteristics of the microorganismãNon-motileãDoes not ferment lactose ãGas is not produced from glucose fermentationãIMViCis -+--ãDoes not produce lysine decarboxylaseãH 2 S and ureasenegative  Shigella  ãSimilar resistance and growth patterns to those of other enterobacteriaceae  –Growth at 7 –40°C, optimum of 35-37°C –Poor survival al pH <4.5 ãGenerally regarded as fragile organisms  –Cannot survive outside the intestinal environment –Wrong. They can survive and grow in different foods Growth of  Shigella  on cubed papaya From Escartinet al., J. Food Prot. 52:471, 1989  0123450 2 4 6Hours at 25-27°C    L  o  g   C   F   U   /  c  u   b  e   (   1   2  c  m    2    ) S. sonnei S. flexneri S. dysenteriae  Shigellosis ã S. dysenteriae  produces a neurotoxin called shigatoxin, which produces a severe syndromeãShigellosis consists of a dysenteric syndrome  –Bacillary dysentery –Invasive virulence mechanism ãIncubation period of 7 h to 7 days  –~36 h in foodborne shigellosis ãLow infective dose  –10-100 cells  Foods associated with shigellosis in the U.S. 18%7%9%29%37% SaladsSeafoodMexican foodOthersUnknown Methods of detection ãEnrichment in GN brothãPlating in selective and differential media  –XLD, McConkey, SS ãBiochemical and serological ID Yersiniaenterocolitica  ãGenus Yersinia   – Y. pestis  ãBubonic plague  – Y. pseudotuberculosis  ãMesenteric adenitis  – Y. enterocolitica  ãGastroenteritis  Y. enterocolitica  ãCharacteristics of the organism  – Enterobacteriaceae  family –Psychrotroph ãGrows From -1 to 40°CãOptimum 29°C  –Motility depends on temperature ãMotile at 25°CãNon-motile at 35°C  –pH ãMinimum 4.1 –5.1 depending on acidulantãOptimum 7 -8 Y. enterocolitica  ãIsolated from different environments  –Soil –Fresh water –Intestinal tract of many animals ãHas been found in many foods  –Milk and milk products –Meats –Pork in particular –Poultry –Fish and shellfish –Fruits and vegetables Y. enterocolitica  ãNot a common disease in the United StatesãIncubation period of 1 –11 days  –Lasts between 5 and 14 days ãCommon syndrome includes self-limiting gastroenteritis  –Fever –Abdominal pain –Sometimes mistakenly diagnosed as appendicitis ãOther forms of yersiniosis  –Septicemia –Arthritis
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