E.coli & associated Infections

Question 1

E.Coli General Info

Answer 1

• Part of Normal Colon flora
• Intestinal Infections (ETEC/EHEC)
• Extraintestinal Infections (UTI…)

Question 2

E.Coli Morphology

Answer 2

• Gram Negative
• Rods
• Flagellated
• Pilli

Question 3

E.Coli Cultivation

Answer 3

• Grow on simple Agar
• EMB agar green metallic shine from Lactose fermentation

Question 4

E.Coli Biochemical Properties

Answer 4

• Lactose +
• Indol +
• Urease -

Question 5

E.Coli Virulence Factors

Answer 5

• Polysaccharide Capsule (K-antigen)
• Adhesins
• Flagella
• Endo/Exo-Toxins
• Hemolysins

Question 6

E.Coli Intestinal Diseases Strains

Answer 6

• Enteroinvasive E.Coli (EIEC)
• Enteropathogenic E.Coli (EPEC)
• Enteroaggregative E.Coli (EAEC)
• Enterotoxic E.Coli (ETEC)
• Enterohemorrhagic E.Coli (EHEC)

Question 7

Enteroinvasive E.Coli (EIEC)

Answer 7

• Direct invasion & destruction of intestinal epithelium (like shigella)
• Acquired virulence from Shigella
• Bloody Mucoid Diarrhea, Dysentery
• Acts in Large intestine
  (mostly children)

Question 8

Enteropathogenic E.Coli (EPEC)

Answer 8

• Destruction of Microvilli
• Inhibition of absorption (less SA)
• Watery Diarrhea & Vomiting
• Common in Children <1 year

Question 9

Enteroaggregative E.Coli (EAEC)

Answer 9

• Attachment/Aggregation to epithelial cells
• Cytokine release, Neutrophils, Diarrhea
• Watery Diarrhea with inflammatory cells, fever, vomiting, abdominal pain
• Often prolonged

Question 10

Enterotoxic E.Coli (ETEC)

Answer 10

• Produce enterotoxin acquired from cholera
• Heat Labile ET: cAMP increase, large vol. watery diarrhea, Travelers Diarrhea (bali belly)
• Heat Stable ET: cGMP increase, less water and electrolytes
• Contaminated water/food

Question 11

Enterohemorrhagic E.Coli (EHEC)

Answer 11

• Produces Shiga-like Toxin (inh. protein synth)
• Most important O157:H7 strain
• Undercooked meat
• Severe, Bloody Diarrhea, No fever
• Hemolytic Uremic Syndrome (HUS): Autoimmune thrombotic Microangiopathy

Question 12

E.Coli Extraintestinal Diseases

Answer 12

• UTI (#1 cause), Cystitis, Pyelonephritis
• Neonatal Meningitis (K1 serotype)
• Sepsis (LPS)
• Nosocomial Infections (ESKAPE)

Question 13

E.Coli Treatment

Answer 13

• Rehydration (for intestinal)
• ESBL: Carbapenems
• MBL/CRE: Colistin
• UTI: Fosfomycin, Nitrofurantoin, SXT-TMP
• Meningitis: Ceftriaxon

Question 14

E.Coli Microbiological Diagnosis

Answer 14

• Significant Bacteriuria (>10^5 CFU/ml)
• Lactose positive on EMB agar
• Indole +
• Urease -