Ecoli_UG_lecture.ppt it expane the E coli very good
- 1. E. coli Prof. Jyotsna Agarwal Dept. Microbiology KGMU
- 2. E. coli • Present in GUT- Normal flora • Endogennous • Belongs to enterobacteriacae family
- 3. Identification • Gram negative rod • Motile • Capsule may be found in some strains • Does not form spores
- 4. • Aerobe and facultative anaerobe • Optimum temperature for growth 37C • Tolerates bile salt, Grows on MacConkey agar forms pink colour colonies due to lactose fermentation IMViC + + - - (Indole, methyl red, VP, Citrate
- 6. Antigenic structure • O somatic • H flagellar • K capsular • K has a strong association with virulence, particularly meningitis, pyelonephritis
- 7. Factors of pathogenicity and virulence • Endotoxin • Capsule • Antigenic variation • Exotoxin- Hemolysins, Enterotoxins- LT, ST, VT • Adhesins, fimbriae
- 8. Infections • Urinary tract infection • Diarrhoea • Pyogenic/wound infection-post surgical • Septicemia • Neonatal meningitis
- 9. Urinary tract infections • E. coli is the most common cause of UTI • Account for 90% of cases in sexually active women, Why? • Ascending infection • Symptoms- ?
- 10. Types of diarrheagenic E.coli • ETEC entero toxic E. coli • EIEC- entero invasive E. coli • EPEC enetro pathogenic • EAEC entero aggregative • EHEC entero haemorrhagic- some strains can cause “Hemolytic uremic syndrome”
- 11. • LT–is heat labile and binds to specific Gm11 gangliosides on epithelial cells of small intestine where it stimulates production of cAMP. • Increased cAMP opens up chloride channel, leading to Cl secretion in to bowel lumen. Sodium follows to maintain electroneutrality. Resulting in secretory diarrhoea which is watery.
- 12. • Produce 2 types of enterotoxin: LT & ST • Entero toxigenic E coli is common cause for travellers diarrhoea and watery diarrhoea in children. Entero toxigenic E. coli (ETEC)
- 13. Entero pathogenic E. coli (EPEC) • Important cause of diarrhoea in infants of developing countries. • Adhere to mucosal cells in small bowel, lead to loss of microvilli, result in watery diarrhoea. • Normally do not produce toxins, NON INVASIVE
- 14. Entero hemorrhagic E. coli (EHEC) • Produce verotoxin (VT) also called Shiga like toxin. • Toxin acts systemically- vascular endothelium • Clinically it can cause mild to severe form of diarrhoea with hemorrhagic colitis, and potentially fatal Hemolytic uremic syndrome in young children and elderly • Typical example is E coli O157:H7,
- 15. Entero invasive E. coli (EIEC) • Produces disease similar to shigella • Commonly affect children in developing countries and travellers. • Disease is due to invasion in to mucosal cells of intestine. Bacteria multiply inside epithelial cells and destruction/ inflammation /ulceration occurs with bloody diarrhoea with mucus and necrotic tissue
- 16. Entero aggregative E. coli (EAEC) • Produce acute/chronic diarrhoea in persons in developing countries.
- 18. summary • Normal flora of gut, Endogennous infection • Most common cause of urinary tract infection • Other infections- • Gastroenteritis (diff types of E. coli) • Neonatal meningitis • Hemolytic uremic syndrome • Wound infection (eg. GI surgery sepsis)