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ENTEROBACTERIACEAE (ENTEROBACTERIA; COLIFORMS)

ENTEROBACTERIACEAE (ENTEROBACTERIA; COLIFORMS). Ali Somily MD,FRCPC. Escherichieae Klebsielleae Proteus Entrobacter Citrobactereae Serratia Hafnia. Yersinieae Providencia Morganella Edwardsielleae Salmonelleae Shigella Ewinia Pictinobacterium. Classification 15 Genera.

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ENTEROBACTERIACEAE (ENTEROBACTERIA; COLIFORMS)

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  1. ENTEROBACTERIACEAE(ENTEROBACTERIA; COLIFORMS) Ali SomilyMD,FRCPC

  2. Escherichieae Klebsielleae Proteus Entrobacter Citrobactereae Serratia Hafnia Yersinieae Providencia Morganella Edwardsielleae Salmonelleae Shigella Ewinia Pictinobacterium Classification15 Genera

  3. Incidence of Enterobacteriaceae Associated with Bacteremia

  4. General Characteristics: • Small GNB, Non – spore forming grow on MacConkey • Facultative anaerobic. • Grow readily at 35oC except Yersinia(25o-30oC) • Colony ;hemolysis swarming, • All glucose fermenter with strong acid and gas formation • Catalase positive • Oxidase negative. • Reduce Nitrate to nitrite • Some may be motile peritrichous flagella / Non- motile S&K • Capsulated / Non- capsulated.

  5. Growth Characteristics: • Non – fastidious  grow on all types of media. • Grow in the presence of bile acids and salts: • Advantage taken of this to prepare selective media for Coliforms. • E.g. MacConkey agar contains bile acid and therefore selects Coliforms over other organisms. • E.g. A Strep that do not survive the presence of bile acids, • Additionally these selective media contain lactose and pH indicator to differentiate lactose fermenters (LF) from non- lactose fermenters (NLF).

  6. Biochemical Reactions • All enterobacteria ferment glucose and various other sugars to produce acid; • some also produce gas during the fermentation.

  7. Media Enrichments Inhibitors pH indicators Protein hydrolysates Carbohydrates Buffers

  8. Selective media

  9. MAC Lactose- fermenter

  10. MacConkey agar

  11. Sulfide indole motility (SIM) Sulfide indole motility (SIM)

  12. IMViC E. coli (+ + - -). Entero/Kleb(- -++)

  13. Ortho-nitrophenyl-(3-D-galactopyranoside (ONPG) initial degradation of lactose

  14. Lysine iron agar (LIA) Decarboxylate Non Deaminate

  15. Tubes of motility medium

  16. E.coli IMViC Shigella Nonmotile E.coli Yersinea Urea + E.coli Edwardasiella H2S E.coli Salmonella Indol – E.coli Citrobacter Lysin – Salmonella Proteus Lysin- Urea + Salmonella Summary

  17. Hydrogen Sulfide-Positive Edwardsiella tarda Proteus vulgaris Salmonella species Citrobacter freundii Voges-Proskauer-Positive Proteus mirabilis Klebsiella species Pantoea species Enterobacter species Hafnia species Serratia species Phenylalanine Deaminase-Positive Proteus species Morganella species Nonmotile at 36°C Providencia species Shigella species Klebsiella species Yersinia species (motile at 22°C) KEY FACTS TO REMEMBERFOR IDENTIFYING ENTEROBACTERIACEAE

  18. Antigenecity Coliforms often subtype on the basis of 3 structural antigens: • Cell wall - Lipopolysaccharide: Somatic ‘O’ antigens • Flagella (for motile organisms)  Flagellar ‘H’ antigens • Capsular (for capsulated organisms) ‘K’ antigens. Special ‘K’ antigen found in Salmonella typhi called Vi.

  19. S. typhi O antigen side chain (Fimbriae)

  20. Structure of Lipopolysaccharide

  21. Structure of Lipid A • Hydrophobic Lipid A is endotoxic component

  22. 1. Virulence Factors: • Endotoxin Lipopolysaccharide:- Polysaccharide: antigenic Lipid A: toxic • Capsule Antiphagocytic • Pili For attachment. Best known pili or K 88 of E.coli strains causing diarrhea in infant pigs. • Enterotoxin by s species especially E. coli causing diarrhea.

  23. EXOTOXIN • 1. Released from the cell before • or after lysis • 2. Protein • 3. Heat labile • 4. Antigenic and immunogenic • 5. Toxoids can be produced • 6. Specific in effect on host • 7. Produced by gram-positive and gram-negative organisms • ENDOTOXIN • 1. Integral part of cell wall • 2. Endotoxin is LPS; Lipid A is toxic component • 3. Heat stable • 4. Antigenic; ??immunogenicity • 5. Toxoids cannot be produced • 6. Many effects on host • 7. Produced by gram-negative organisms only

  24. 2. Habitat • Saprophytic found free living in soil, water, plants etc. i.e. In the environment • Intestines of man and animals generally as part of the normal flora. Predominant aerobic normal intestinal flora.

  25. 3. Diseases Produced • a. Intestinal • b. Extra intestinal

  26. a. Intestinal • Salmonella & Shigella • primary intestinal pathogens • E.coli • facultative intestinal pathogen

  27. b. Extra intestinal • U.T.I. - together, Coliforms contribute up to 80% of all U.T.I. • Septicaemia • Meningitis especially in neonates and also associated with surgery/ trauma. • Respiratory tract infection • Wound infections - especially post –operative.

  28. Klebsiella pneumoniae • Classic cases of pneumonia, characterized by production of brick-red or "currant jelly" sputum, were known to be caused by Friedlander's bacillus

  29. E.COLI DIARRHAE • Only about 10 -15% of strains of E. coli associated with diarrhea. • Types of E. coli diarrhea • Enterotoxigenic E. coli (E T E C) • Enteropathogenic E. coli (E P E C) • Enteroinvasive E. coli (E I E C) • Enterohaemorrhagic E. coli (E H E C )

  30. Enterotoxigenic E. coli (E T E C) • Production of plasmid mediated enterotoxin: • 2 TYPES of ENTEROTOXIN: • Heat labile (LT) through C. AMP • Heat stable (ST) through C. GMP • Strains attached to duodenal mucosa through their pili, enterotoxin produced  Diarrhoea. • Also known as Traveler's Diarrhoea because these strains are one of the group of microorganisms that cause diarrhoea in travellers.

  31. Enterotoxigenic E. coli • Heat labile toxin • like choleragen • Adenylcyclase activated • cyclic AMP • secretion water/ions • Heat stable toxin • Guanylatecyclase activated • cyclic GMP • uptake water/ions

  32. Enteropathogenic E. coli (E P E C) • Confined to infants and children up to age of 18 months to 2 years. • No cases occur after 2 years. • Associated with bottle feeding. • Outbreaks occur in nurseries. • Site of action: again in the duodenum. • Strains adhere to duodenal mucosa with pili. • Mechanism for diarrhoea not known.

  33. Enteroinvasive E. coli (E I E C) • Strains actively invade colonic mucosa and cause dysenteric–like diarrhoea.

  34. Enterohaemorrhagic E. coli (E H E C ) • Best known is E. coli serotype 0157, H7 strain; produces toxin referred to as verocytotoxin and mechanism of action similar to the toxin of Sh. Dysenteriae I and also causes bloody diarrhoea. • Site of action mainly ascending and transverse colon.

  35. SOURCES OF INFECTION: • Reservoir: Intestine of animal • Uncooked meatespecially beef, poultry, pork,burgers- beef burgers, unpasteurized milk, cheese • Person – to – person transfer.

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