- Presence in drinking water is considered evidence of fecal contamination

- Used as index of fecal pollution

EPIDEMIOLOGY

UTI: perineum

- In women, is associated with sexual activity (honeymoon cystitis)

- A prominent cause of gastroenteritis

- Fecal-oral transmission among infants in hospital nurseries

- Food-borne transmission

SEROLOGY

- somatic (cell wall)

SEROLOGY

- flagellar

- Test for invasiveness of Entero-invasive E. coli

- Procedure: Inoculating the bacteria into the cornea of laboratory animals (e.g., guinea pigs)

- (+) Severe mucopurulent conjunctivitis and severe keratitis

VIRULENCE FACTORS

- Adhesins: Colonization factor antigens (CFA/I,CFA/II, CFA/III)

- Exotoxins: Heat-labile toxin (LT-1); heat-stable toxins (Sta)

VIRULENCE FACTORS

- Adhesins: BFP (Bundleformingpili); intimin

- Exotoxins: none

VIRULENCE FACTORS

- Adhesins: Aggregative adherence fimbriae(AAF/I, AAF/II,AAF/III)

- Exotoxins: Entero-aggregative heat-stable toxin; plasmid-encoded toxin

VIRULENCE FACTORS

- Adhesins: BFP; intimin

- Exotoxins: Shiga toxins (Stx1,Stx2)

VIRULENCE FACTORS

- Adhesins: Invasive plasmid antigen

- Exotoxins: Hemolysis (HlyA)

Virulence Factors for UTI

Virulence Factors for UTI

- Mannose sensitive

- Bind to mannose-containing receptor

- Probably responsible for anchoring E. coli to mucus in large intestine and contributes to colonization of the vaginal tract

Virulence Factors for UTI

Named for ability to agglutinate human RBCs carrying the P blood group antigen

Virulence Factors for UTI

In uropathogenic strains of E. coli

Virulence Factors for UTI

- Lyses erythrocytes and other cell types

- Cytokine release & stimulation of inflammatory response

Virulence Factors for Neonatal Meningitis

Virulence Factors for Neonatal Meningitis

- Commonly present in GI tracts of pregnant women and newborn infants

- Also common in strains causing septicemia and UTI

- Antiphagocytic: provides resistance against complement-mediated lysis

Virulence Factors for Neonatal Meningitis

- Bind to vascular endothelium and epithelial lining of brain tissues

Clinical Manifestation

- Commonly originates from infections in the urinary or GI tract

- Major strain associated: E. coli O25b Sequence Type 131

E. coli-associated Diarrheal Disease

- Epidemiology: Hemorrhagic colitis and HUS in all ages

- Type of diarrhea: Bloody or non-bloody

- Pathogenic mechanism: Shiga toxin production; large bowel adherence, coagulopathy

E. coli-associated Diarrheal Disease

- Epidemiology: Acute and chronic endemic and epidemic diarrhea in infants.

- Type of diarrhea: Watery

- Pathogenic mechanism: Small bowel adherence and

effacement

E. coli-associated Diarrheal Disease

- Epidemiology: Infant diarrhea (in resource lmtd. Countries) and traveler's diarrhea in all ages

- Type of diarrhea: Watery

- Pathogenic mechanism: Small bowel adherence, LT &/or STa enterotoxin production.

E. coli-associated Diarrheal Disease

- Epidemiology: Diarrhea with fever in all ages

- Type of diarrhea: Bloody or non-bloody; dysentery

- Pathogenic mechanism: Mucosal Invasion and Inflammation of large bowel

E. coli-associated Diarrheal Disease

- Epidemiology: Acute and chronic diarrhea in all ages

- Type of diarrhea: Watery, occ. bloody

- Pathogenic mechanism: Small and large bowel adherence, enterotoxin and cytotoxin production

E. coli major groups that cause gastroenteritis

Small Intestines

E. coli major groups that cause gastroenteritis

Large Intestines

Diarrhea in infants and children

- Infection is initiated by bacterial attachment to epithelial cells of small intestine, leading to subsequent destruction/effacement of microvilli bacterial proteins are actively secreted into the host cell

→ One such protein is the translocated intimin receptor

Defined by the following:

− Presence of LEE

− Absence of Shiga toxin (differentiates it from Shigatoxin-producing E. coli)A

- Associated with multiple specific serotypes of E. coli (identified by O antigen and H antigen [occasionally] typing)

- Requires 2 important factors:

▪ Bundle-forming pilus

▪ Chromosomal Locus of Enterocyte Effacement (LEE) pathogenicity island

Enteropathogenic E. coli (EPEC) Virulence Factors

- Encoded by plasmid EPEC adherence factor (EAF)

- Basis for classification into typical and atypical strains

Enteropathogenic E. coli (EPEC) Virulence Factors

- Promotes tight adherence characteristic of EPEC (attachment and effacement)

- Contains virulence genes

Strains DO NOT produce heat-labile toxin (LT) or heat stable toxin (ST) unlike ETEC

Oral non-absorbable antibiotics for Enteropathogenic E. coli (EPEC)

Important cause of traveler's diarrhea (secretory diarrhea) and diarrhea in children less than 5 years old in developing countries

Prerequisites for disease

- Susceptible individual (no Ab to enterotoxins)

- Adherence (plasmid-encoded adhesins)

- Enterotoxin production (plasmid encoded toxin genes)

Pathogenicity & Virulence Factors

- Colonization Factors

- Enterotoxins (2 plasmid-mediated enterotoxins)

▪ Heat-labile Enterotoxin (LT)

▪ Heat-stable Enterotoxin (STa)

- LAGS

▪ Labile - cAMP

▪ Stable - cGMP

ETEC Virulence factors

- Act as ligands binding bacteria to specific complex

carbohydrate receptors

- Found only in strains that cause diarrheal disease

ETEC Virulence factors

- cAMP → hypersecretion of water and electrolytes into the bowel lumen → profuse, watery, non-inflammatory diarrhea

- Antigenic and cross-reacts with enterotoxin of V. cholera

- Result:

1. hypersecretion of water andchlorides

2. Inhibition of reabsorption of sodium.

ETEC Virulence factors

- Accumulation of cGMP inhibits intestinal fluid uptake → net fluid secretion

ETEC Treatment

Current DOC since Vaccines are NOT available

- Produce a disease very similar to shigellosis

- Produce disease by invading intestinal mucosal epithelial cells

Strains are:

- Non-lactose or late lactose fermenters

- Non-motile® Cross-react with certain Shigella O antigens

- However, do not produce Shiga toxin

- Acute and chronic diarrhea persons in developing countries

- "Stacked brick" appearance mediated by AAF1 (Aggregative adherence fimbriae 1)

- Toxins: enteroaggregative heat stable toxin and plasmid-encoded toxin

- Effect: induction of fluid secretion

− aka verotoxin-producing E. coli (VTEC)

− Causes hemorrhagic colitis and hemolytic uremic syndrome (HUS)

EHEC Epidemiology

- Most common Shiga-toxin producing E. coli serotype and can be identified in clinical specimens

EHEC Epidemiology

Disease is distinct from bacillary dysentery caused by Shigella and EIEC because there is no fever, and the stool is bloody and copious

EHEC Epidemiology

E. coli O157:H7 Organism has been isolated from dairy cattle, calves, chicken, swine, and sheep. INFECTED ANIMALS MANIFEST SICKNESS

EHEC Epidemiology

Transmission of EHEC

EHEC Pathogenicity & Virulence Factors

Essentially identical to the Shiga toxin produced by Shigella dysenteriae

EHEC Pathogenicity & Virulence Factors

Bind to Gb3 (globotriaosylceramide; a glycolipid) found in high concentrations in intestinal villi and renalendothelial cells

EHEC Pathogenicity & Virulence Factors

Binds to 28S rRNA → cessation of protein synthesis

EHEC Pathogenicity & Virulence Factors

Associated with production of Stx2 → destruction of glomerular endothelium → platelet activation & thrombin deposition → ↓ GFR; acute renal failure

Treatment & Prevention of EHEC

E. coli culture

- Medium of choice for isolation and culture

- Produces a greenish metallic sheen

E. coli culture

- Medium of choice for isolation and culture

- Turns the agar plate pink, like all lactose fermenters

E. coli cultures

Slightly selective and differential medium for E. coli

(+/-)

- Indole

- Methyl Red

(+/-)

- Voges Proskauer

- Citrate

(+/-)

- Lysine

- Acetate

- Lactose