enterobacteriaceae (enterobacteria; coliforms)

ENTEROBACTERIACEAE(ENTEROBACTERIA;

COLIFORMS)

Ali SomilyAli Somily MD,FRCPCMD,FRCPC

ClassificationClassification15 Genera 15 Genera

EscherichieaeEscherichieae KlebsielleaeKlebsielleae Proteus Proteus EntrobacterEntrobacter CitrobactereaeCitrobactereae SerratiaSerratia HafniaHafnia

Yersinieae Yersinieae ProvidenciaProvidencia MorganellaMorganella EdwardsielleaeEdwardsielleae SalmonelleaeSalmonelleae ShigellaShigella EwiniaEwinia PictinobacteriumPictinobacterium

Incidence of Enterobacteriaceae Associated with Bacteremia

General Characteristics: Small GNB, Non – spore forming grow on MacConkey Facultative anaerobic. Grow readily at 35Grow readily at 35ooC except C except Yersinia Yersinia (25(25oo--

3030ooC)C) 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 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)Lysine iron agar (LIA)

E.coliE.coli IMViCIMViC

ShigellaShigella Nonmotile E.coliNonmotile E.coli

YersineaYersinea Urea + E.coliUrea + E.coli

EdwardasiellaEdwardasiella H2S E.coliH2S E.coli

SalmonellaSalmonella Indol – E.coliIndol – E.coli

CitrobacterCitrobacter Lysin – SalmonellaLysin – Salmonella

ProteusProteus Lysin- Urea + Lysin- Urea +

SalmonellaSalmonella

KEY FACTS TO REMEMBERFOR 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. Endotoxin Lipopolysaccharide:-Lipopolysaccharide:-Polysaccharide: antigenicPolysaccharide: antigenicLipid A: toxic Lipid A: toxic

B. Capsule Antiphagocytic

C. PiliFor attachment.For attachment.Best known pili or K 88 of E.coli strains causing diarrhea in infant Best known pili or K 88 of E.coli strains causing diarrhea in infant

pigs.pigs.

D. Enterotoxinby s species especially E. coli causing diarrhea.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. Saprophytic found free living in soil, water, plants etc.

i.e. In the environment

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

1.1. U.T.I. - together, Coliforms contribute up to 80% U.T.I. - together, Coliforms contribute up to 80% of all U.T.I.of all U.T.I.

2.2. SepticaemiaSepticaemia3.3. Meningitis especially in neonates and also Meningitis especially in neonates and also

associated with surgery/ trauma.associated with surgery/ trauma.4.4. Respiratory tract infectionRespiratory tract infection5.5. Wound infections - especially post –operative.Wound infections - especially post –operative.

Klebsiella pneumoniaeKlebsiella pneumoniae

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

E.COLI DIARRHAEE.COLI DIARRHAE

Only about 10 -15% of strains of E. coli associated with diarrhea.

Types of E. coli diarrhea1. Enterotoxigenic E. coli (E T E C)

2. Enteropathogenic E. coli (E P E C)

3. Enteroinvasive E. coli (E I E C)

4. Enterohaemorrhagic E. coli (E H E C )

EEnterotoxigenic 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 Enterotoxigenic E. coliE. coli Heat labile toxinHeat labile toxin

like choleragenlike choleragen Adenyl cyclase activated Adenyl cyclase activated cyclic AMP cyclic AMP secretion water/ionssecretion water/ions

Heat stable toxinHeat stable toxin Guanylate cyclase activated Guanylate cyclase activated cyclic GMPcyclic GMP uptake water/ionsuptake 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::

Reservoir: Intestine of animal : Intestine of animal UUncooked meat especially beef, poultry, pork,burgers-

beef burgers, unpasteurized milk, cheese

Person – to – person transfer.