ENTEROBACTERIACEAE (ENTEROBACTERIA; COLIFORMS) Ali Somily MD,FRCPC

Classification 15 Genera Escherichieae Escherichieae Klebsielleae Klebsielleae Proteus Proteus Entrobacter Entrobacter Citrobactereae Citrobactereae Serratia Serratia Hafnia Hafnia Yersinieae Providencia Morganella Edwardsielleae Salmonelleae Shigella Ewinia Pictinobacterium

Incidence of Enterobacteriaceae Associated with Bacteremia

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

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).

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

Sulfide indole motility (SIM)

Lysine iron agar (LIA)

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

KEY FACTS TO REMEMBER FOR IDENTIFYING ENTEROBACTERIACEAE 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)

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. Antigenecity

S. typhi O antigen side chain (Fimbriae)

Structure of Lipopolysaccharide

Structure of Lipid A  Hydrophobic Lipid A is endotoxic component

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

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 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

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

3.Diseases Produced a.Intestinal b.Extra intestinal

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

b.Extra intestinal 1. U.T.I. - together, Coliforms contribute up to 80% of all U.T.I. 2. Septicaemia 3. Meningitis especially in neonates and also associated with surgery/ trauma. 4. Respiratory tract infection 5. Wound infections - especially post –operative.

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

E.COLI DIARRHAE Only about % 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 )

E 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.

Enterotoxigenic E. coli Heat labile toxin Heat labile toxin like choleragen like choleragen Adenyl cyclase activated Adenyl cyclase activated cyclic AMP cyclic AMP secretion water/ions secretion water/ions Heat stable toxin Heat stable toxin Guanylate cyclase activated Guanylate cyclase activated cyclic GMP cyclic GMP uptake water/ions uptake water/ions

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.

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

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.

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