2/16/2016 Learning Objectives Food 1. Use basic biochemical characteristics to identify Micrbiology Escherichia coli 0157:H7 2.Understand what conditions in foods favor the growth of E coli0157:H7 Chapter 12 AN INTRODUCTION Enterohemorrhagic 4. Choose appropriate interventions to prevent the Escherichia coli growth of E coli0157:H7 5.Identify environmental sources of E coliO157:H7 6.Understand the roles of E.coli O157:H7 toxins and virulence factors in causing foodborne illness 7.Become familiar with newly emerging Shiga toxin- produ cing E.colistrains tes with creater than i cos States with and >10 cases Outbreak Outbreak Eating raw cookie dough Dutch-style Gouda cheese Summer 2009 November 2010 65 people became infected with Escherichia coli 157:H7 after eating Nestle Toll Hou 38 people from 5 states became infected with use cookie E.coli0157:H7 after eating Dutch-style Gouda dough cheese 25 people were hospitalized Strain was isolated from unopened packages 7 developed hemolytic-uremic syndrome (HUS) found at a store in New Mexico 70%of those ill were under 19 years old ·No deaths The only outbreak of E colij0157:H7 associated 1 person developed hemolytic-uremic syndrome with cookie dough (HU5) Solution?Wait until the cookies are cooked. Any type of food can carry this pathogen 2
2/16/2016 1 Chapter 12 Enterohemorrhagic Escher ch a col ichia coli Learning Objectives 1. Use basic biochemical characteristics to identify Escherichia coli O157:H7 2. Understand what conditions in foods favor the growth fo E li . co O157 H7 O157:H7 3. Recognize, from symptoms and time of onset, a case of foodborne illness caused by E. coli O157:H7 4. Choose appropriate interventions to prevent the growth of E. coli O157:H7 5. Identify environmental sources of E. coli O157:H7 6. Understand the roles of E. coli O157:H7 toxins and virulence factors in causing foodborne illness 7. Become familiar with newly emerging Shiga toxinproducing E. coli strains Outbreak Eating raw cookie dough States with greater than 1 case Summer 2009 • 65 people became infected with Escherichia coli O157:H7 after eating Nestle Toll House cookie dough • 25 people were hospitalized • 7 d l d h l developed hemolytic-uremic d (H ) syndrome (HUS) • 70% of those ill were under 19 years old • The only outbreak of E. coli O157:H7 associated with cookie dough • Solution? Wait until the cookies are cooked. Outbreak Dutch-style Gouda cheese States with 1-9 cases and >10 cases November 2010 • 38 people from 5 states became infected with E. coli O157:H7 after eating Dutch-style Gouda cheese • Strain was isolated from unopened packages found at a store in New Mexico • No deaths • 1 person developed hemolytic-uremic syndrome (HUS) • Any type of food can carry this pathogen
2/16/2016 01 Foods or food han- Outbreak dling practices implicated or the riskacqu Fresh spinach outbreaks Summer 2006 nderkd udbeef 206 people in 25 states 4量n量中中 became infected with E.coli0157:H7 after 融高 t行cured s0hT eating fresh spinach Lettuce ·3 people died Pruc rmmd Wild pigs captured in the area where the spinach was grown tested positive for the E.coliO157:H7 Ras幼spo,af6spo strain associated with the bagged spinach. FDA emphasized the need for good agricultural ate practices. Categories of Escherichia coli Escherichia coli Diarrheagenic E.colis categorized into groups based on All categories of E.colimay be shed in the virulence factors feces of infected humans. pathogenicity -spread to other humans clinical syndromes -spread to animals -distinct O:H serotypes -spread to the environment E.coli is differentiated by three major surface antigens >O-antigens Lipopolysaccharide >H-antigens Flagella >K-antigens Capsule 2
2/16/2016 2 Outbreak Fresh spinach Summer 2006 • 206 people in 25 states became infected with E. coli O157:H7 after eating fresh spinach • 3 p p eo le died • Wild pigs captured in the area where the spinach was grown tested positive for the E. coli O157:H7 strain associated with the bagged spinach. • FDA emphasized the need for good agricultural practices. Categories of Escherichia coli • Diarrheagenic E. coli is categorized into groups based on - vil fts irulence factors - pathogenicity - clinical syndromes - distinct O:H serotypes • E. coli is differentiated by j three major surface antigens O-antigens Lipopolysaccharide H-antigens Flagella K-antigens Capsule Escherichia coli • All categories of E. coli may be shed in the feces of infected humans. - spread to other humans - spread to animals - spread to the environment
2/16/2016 ETEC Enterotoxigenic E.coli Major cause of infantile diarrhea in developing countries Most frequently the cause of traveler's diarrhea Colonizes the small intestine via fimbrial adhesion factors Produces heat-labile or heat-stable enterotoxin that causes fluid accumulation and diarrhea Humans are the principle reservoir of strains that cause human illness Scanning electron microscopy image showing attachment of pathogenic E.co/ito human EIEC Enteroinvasive E.coli epithelial cells Causes non-bloody diarrhea and dysentery similar to Shigella Invades and multiplies within intestinal epithelial cells causing cell death A large virulence plasmid encodes several outer membrane proteins required for invasion Site of colonization is the colon Humans are the main reservoir Main serogroup is 0124
2/16/2016 3 ETEC Enterotoxigenic E. coli • Major cause of infantile diarrhea in develop g in countries • Most frequently the cause of traveler’s diarrhea • Colonizes the small intestine via fimbrial adhesion factors • Produces heat-labile or heat-stable enterotoxin that causes fluid accumulation and diarrhea • Humans are the principle reservoir of strains that cause human illness Scanning electron microscopy image showing attachment of pathogenic E. coli to human epithelial cells EIEC Enteroinvasive E. coli • Causes non-bloody diarrhea and dysentery similar to Shigella • Invades and multiplies within intestinal epithelial cells causing cell death • A large virulence plasmid encodes several outer membrane proteins required for invasion • Site of colonization is the colon • Humans are the main reservoir • Main serogroup is O124
2/16/2016 EPEC Enteropathogenic E.coli EAEC Enteroaggregative E coli Causes severe diarrhea Associated with persistent diarrhea in in infants infants and children ·Associated with Differ from other E.coli due to their outbreaks in nurseries Humans are main aggregative adherence pattern on cells reservoir Appears like stacked bricks on cell Induces lesions in cells Bacteria are attached to surfaces to which they adhere cup-like projections at A gene probe derived from a plasmid Invade epithelial cells the cell membrane. Localized destruction of associated with this strain is available microvilli (MV) EAEC Enteroaggregative E.coli DAEC Diffusely Adhering E.coli Associated with diarrhea in young children older than infants Risk increases with age from 1-5 years ·Why is unknown Mild diarrhea without blood Adheres randomly to epithelial cells Patterns of HeLa cell adherence of EAEC strains Does not produce enterotoxins or shiga toxins (A)Negative control (X400) (B)aggregative adherence(X1000)
2/16/2016 4 EPEC Enteropathogenic E. coli • Causes severe diarrhea in infants • Associated with outbreaks in nurseries • Humans are main reservoir • I d l i i ll Induces lesions in cells to which they adhere • Invade epithelial cells - Bacteria are attached to cup-like projections at the cell membrane. - Localized destruction of microvilli (MV) EAEC Enteroaggregative E. coli • Associated with persistent diarrhea in i f t d hild infants and children • Differ from other E. coli due to their aggregative adherence pattern on cells • Appears like stacked bricks on cell surfaces • A gene probe derived from a plasmid associated with this strain is available EAEC Enteroaggregative E. coli Patterns of HeLa cell adherence of EAEC strains (A) Negative control (X400) (B) aggregative adherence (X1000) DAEC Diffusely Adhering E. coli • Associated with diarrhea in young child ld th i f t hildren older than infants • Risk increases with age from 1-5 years • Why is unknown • Mild diarrhea without blood • Adh d l i h li l ll Adheres randomly to epithelial cells • Does not produce enterotoxins or shiga toxins
2/16/2016 EHEC Enterohemorrhagic E.coli Characteristics of E coli First recognized in 1982 E.coli 0157:H7 was identified as the cause of Common microflora in the intestines of two outbreaks of bloody diarrhea. humans and warm-blooded animals Since then,other EHEC serotypes(026,0111) Most strains are harmless are associated with bloody diarrhea. Some strains cause diarrheal disease Serotype 0157:H7 is the main cause of EHEC- associated diseases .167O-antigens,53 H-antigens,and 74 K antigens Non-O157-H7 serotypes are O26:H11,0111:H8. O-and H-antigens are used to serotype E and 0157:NM coljassociated with diarrheal disease Produce verotoxins or Stx toxins(toxin similar to Shiga toxin)that are cytotoxic to cells Characteristics of EHEC 0157:H7 Characteristics of EHEC 0157:H7 Serotype O157:HZ has unique characteristics Acid tolerance compared to other E.coli strains Unlike most foodborne pathogens,serotype Shiga-toxin production 0157:H7 is tolerant of acidic pH does not grow at temperatures >44.5C Minimum pH for growth is pH 4.0 to 4.5 does not ferment sorbitol within 24 h The induced acid-tolerant state may persist does not produce B-glucuronidase and thus for a prolonged period(=28 days)at refrigerated temperatures. cannot hydrolyze MUG -Induced acid tolerance increases tolerance to carries the attaching and effacing gene (eae) other environmental stresses such as heat, carries a large plasmid radiation,and antimicrobials >Alternative sigma factor RpoS induces >200 genes in response to stress
2/16/2016 5 EHEC Enterohemorrhagic E. coli • First recognized in 1982 • E. coli O157:H7 was identified as the cause of two outbreaks of bloody diarrhea. • Since then, other EHEC serotypes (O26, O111) are associated with bloody diarrhea. • Serotype O157:H7 is the main cause of EHECassociated diseases • Non-O157-H7 serotypes are O26:H11, O111:H8, and O157:NM • Produce verotoxins or Stx toxins (toxin similar to Shiga toxin) that are cytotoxic to cells Characteristics of E. coli • Common microflora in the intestines of humans and warm-blooded animals • Most strains are harmless • Some strains cause diarrheal disease • 167 O-antigens, 53 H-antigens, and 74 K antigens • O- and H-antigens are used to serotype E. coli associated with diarrheal disease Characteristics of EHEC O157:H7 • Serotype O157:H7 has unique characteristics compared to other E. coli strains - Shiga-toxin production - does not grow at temperatures >44.5oC - does not ferment sorbitol within 24 h - does not produce -glucuronidase and thus cannot hydrolyze MUG - carries the attaching and effacing gene (eae) - carries a large plasmid Characteristics of EHEC O157:H7 • Acid tolerance - Unlike most foodborne pathogens, serotype O157:H7 is tolerant of acidic pH - Minimum pH for growth is pH 4.0 to 4.5 - The induced acid-tolerant state may persist for a prolonged period ( ≥ 28 days) at refrigerated temperatures. - I d d id t l I n duced acid t olerance i tl t increases t olerance t o other environmental stresses such as heat, radiation, and antimicrobials Alternative sigma factor RpoS induces >200 genes in response to stress