E. Coli Flashcards
What is Enterobacteriacae
- Gram Negative
- Facultatively anaerobic
- Rod shaped
- Ferment glucose to acid and gas
- May or may not ferment lactose
- Habitat: GIT, soil, and water
- 30 genera and >90 species
Which Enterobacteriacae ferment Lactose?
- Escherichia
- Klebsiella
- MacConkey Agar turn pink
Which Enterobacteriacae do NOT ferment lactose
- Salmonella
- Proteus
- Morganella
- Serratia
- Yersinia
- MacConkey Agar stays yellow
What are the most important Genera of Enterobacteriacae?
- Most Common:
- Escherichia: E. coli
- Samonella: S. enterica
- Klebsiella: K. pneumonia
- Less Common:
- Klebsiella aerogenes
- Proteus mirabilis; P. vulgaris
- Morganella morganii
- Serratia marcescens
-
Yersinia:
- Y. pestis
- Y. pseudotuberculosis
- Y. enterocolitica
What are the Coliform Bacteria
- Escherichia coli
- Klebsiella pneumonia
- Klebsiella aerogenes
Where is E. coli found?
- Normal inhabitant of the lower intestinal tract
- Predominant facultative organism
- Soil and water
What are the Antigenic Characteristics of E. coli?
- Somatic (O) (cell wall)
- 187 groups
- lipopolysaccharides
- Endotoxin production - septicemic infection
- Capsule (K)
- Polysaccharide
- Adhesion, protection against phagocytosis
- Flagella (H)
- Protein
- Motility
- Fimbrial/Pilus (F)
- Protein
- Adhesion
How are the pathotypes/virotypes of E. coli classified?
- Intestinal Pathogenic E. coli (IPEC)
- AKA: Diarheagenic E. coli (DEC)
- Extraintestinal Pathogenic E. coli (ExPEC)
What are the categories of IPEC?
- Patterns of attachment on host cells
- singly or in aggregates
- Effects on host cells
- none or destruction
- Production of toxins
- Invasiveness
Enteropathogenic (EPEC)
- Attachment is pili mediated
- Loss of microvilli (effacement)
- Invasion and structural changes
- Produce hemolysin
- Cause diarrhea in hums and animals (pigs)
What hemolysins are produced by E. coli?
- 3 types:
-
Alpha hemolysin (Hly, encoded by hly)
- produced mainly by ETEC and ExPEC
-
Enterohemolysin (Ehx, encoded by ehx)
- Produced by STEC
-
Cytolysin A (ClyA, encoded by clyA)
- Produced by many strains
-
Alpha hemolysin (Hly, encoded by hly)
- Purpose: obtain Iron from lysed RBCs
What is Shiga toxin-producing E. coli?
- STEC, VTEC, or AEEC
- Attachment is mediated by a protein intimin (not pili)
- Loss of microvilli (effacement)
- Invasion and structural changes
- Produces Shiga toxin (Stx)
- ~150 serogroups >400 serotypes
- associated with outbreaks or sporadic diarrheal diseases in humans
- Most common is E. coli O157:H7
What is Shiga Toxin (Stx)?
- 2 subunits: A and B (A-B toxin)
- 2 types:
- Stx1 (100% homology)
- Subtypes: Stx1a, Stx1c, and Stxd
- Stx2 (50% homology)
- subtypes: Stx2a, Stx2b, Stx2c, Stx2d, Stx2e, Stx2f, Stx2g
- Stx1 (100% homology)
- Stx2e involved in edema disease in swine
- Stx2 is more cytotoxic
- Target Cells: Enterocytes and Endothelial cells.
What diseases do STEC infections cause?
- Humans: (O157:H7)
- Hemorrhagic enteritis
- Hemolytic and Uremic syndrome (HUS)
- Food borne
- Pigs:
- Edema disease
- Chickens:
- swollen head syndrome
What are the serotypes of STEC?
- ~150 serogroups and >400 serotypes
- 7 serogroups are more often involved than others
- Most common: O157:H7
- Other major: O26, O45, O103, O111, O121, O145
What is Enteroinvasive E. coli (EIEC)
- Multiply inside the cell
- “Salmonella - like”
- Invasion and cellular destruction
- Cause bacteremia or septicemia
- Mostly seen in poultry (APEC)
What is Enterotoxgenic E. coli? (ETEC)
- ‘Cholera-like’
- Attach (pili mediated) but do NOT invade
- Produce enterotoxins
- Heat labile (LT, 60C or 15 min)
- Heat stable (ST, 100C for 30 min)
- LT is Cholera toxin-like
What are the LT toxins?
- Enterotoxin
- A-B toxin
- 2 types: LT-I and LT-II
What are the ST toxins?
- Enerotoxin
- Small 2kDa proteins
- STa (methanol soluble): fluid accumulation in the intestine
- STb (methanol insoluble)
What is Enteroaggregative E. coli? (EAggEC)
- New group
- Form aggregates (stacked brick adherence)
- Do not invade
- Produce ST-like (heat stable), called “EAST” and hemolysin-like toxins
What is Cytotoxin Necrotizing Factor Producing E. coli? (CNF-PEC)
- Attach but do not invade the cells
- Produce a toxin (CNF) that causes necrosis
- Cause:
- diarrhea in calves, pigs and humans
- Mastitis in cows
- UTI in dogs
What diseases doe Extraintestinal Pathogenic E. coli (ExPEC) cause?
- Septicemia
- Mastitis in dairy cows
- Uterus (Metritis)
- Urinary tract (UPEC)
- Air sacculitis in chickens and turkeys (APEC)
What are the important Virotypes of E. coli in animals?
- ETEC: Intestinal infections (enterotoxins)
- EPEC: Intestinal and extraintestinal infections
- STEC: Edema disease in Pigs (Shiga Toxins)
Who is affected by Intestinal Colibacillosis?
- Piglets
- Calves
- Lambs
- Goat kids
Where does Extraintestinal Colibacillosis occur?
- Septicemic or localized infections in:
- mammary gland
- Urinary tract
- Uterus