Enter Ob Acte Racie

8/2/2019 Enter Ob Acte Racie

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Enterobacteriaceae


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Enterobacteriaceae

normal part of the gut flora found in theintestines of humans and animals, in wateror soil, or are parasites on a animals and

plants

rod-shaped, 1-5 m in length

Gram-negative

aerobes and facultative anaerobes,

ferment sugars to produce acid and or gas
http://en.wikipedia.org/wiki/Gut_florahttp://en.wikipedia.org/wiki/Intestineshttp://en.wikipedia.org/wiki/Parasiteshttp://en.wikipedia.org/wiki/Bacillushttp://en.wikipedia.org/wiki/Gram-negativehttp://en.wikipedia.org/wiki/Facultative_anaerobehttp://en.wikipedia.org/wiki/Fermentation_%28biochemistry%29http://en.wikipedia.org/wiki/Lactic_acidhttp://en.wikipedia.org/wiki/Lactic_acidhttp://en.wikipedia.org/wiki/Fermentation_%28biochemistry%29http://en.wikipedia.org/wiki/Facultative_anaerobehttp://en.wikipedia.org/wiki/Gram-negativehttp://en.wikipedia.org/wiki/Gram-negativehttp://en.wikipedia.org/wiki/Gram-negativehttp://en.wikipedia.org/wiki/Bacillushttp://en.wikipedia.org/wiki/Bacillushttp://en.wikipedia.org/wiki/Bacillushttp://en.wikipedia.org/wiki/Parasiteshttp://en.wikipedia.org/wiki/Intestineshttp://en.wikipedia.org/wiki/Gut_flora


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Properties

reduce nitrate to nitrite.

lack cytochrome C oxidase, exceptions(e.g. Plesiomonas).

Motile by peritrichate flagella or non-motile.

non-spore forming, and non acid fast except for Shigella dysenteriaestrains,

catalase-positive.
http://en.wikipedia.org/wiki/Nitratehttp://en.wikipedia.org/wiki/Nitritehttp://en.wikipedia.org/wiki/Cytochrome_c_oxidasehttp://en.wikipedia.org/wiki/Plesiomonashttp://en.wikipedia.org/wiki/Shigella_dysenteriaehttp://en.wikipedia.org/wiki/Shigella_dysenteriaehttp://en.wikipedia.org/wiki/Plesiomonashttp://en.wikipedia.org/wiki/Cytochrome_c_oxidasehttp://en.wikipedia.org/wiki/Nitritehttp://en.wikipedia.org/wiki/Nitrate


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Properties

Grow readily on ordinary media

Exhibit general biochemical andmorphological similarities

Family- groups/tribes- genera-sub

genera/species- serotypes,biotypes,phagetypes


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Classification

Based on lactose fermentation onMacConkey agar

Lactose fermenters

Non lactose fermenters

Late lactose fermenters


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Classification

Newer systems

Bergeys manual

Kaufmann

Edwards Ewing


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Classification

Tribe 1 : Escherichiae Genus Escherichia Edwardsiella Citrobactor

Salmonella Shigella

Tribe 2 : Klebsielleae Genus klebsiella

Enterobactor Hafnia serratia


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Classification

Tribe 3 :Proteeae

Genus proteus

Morganella

Providencia

Tribe 4 :Erwinieae Genus erwinia


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Escherichia coli

Discovered in 1885 by Theodor Escherich

Intestinal flora

Gram negative straight rod Motile by peritrichate flagella

Non spore forming

Fimbria / capsule +/-
http://en.wikipedia.org/wiki/Theodor_Escherichhttp://en.wikipedia.org/wiki/Theodor_Escherich


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Diarrheal illnessSerologically differntiated

O (somatic of LPS antigen)SerogroupingH (flagella antigen)SerotypingK (capsule antigen


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Cultural characteristics

Aerobes and facultative anaerobes

Grow readily on ordinary media Colony large ,thick, greyish white, moist,

smooth, opaque discs

Rough and smooth variation present Capsule + in pathogenic form
http://en.wikipedia.org/wiki/Facultative_anaerobehttp://en.wikipedia.org/wiki/Facultative_anaerobe


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Cultural characteristics

Hemolysis on blood agar + in pathogenicstrains

Pink colonies on MacConkey media

Liquid broth- general turbidity or heavydeposit


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Biochemical characters

Ferment all sugars except sucroseforming acid and gas

IMViC ---- ++--

No H2S formed

Urea not split

No growth in KCN medium Gelatin not liquified


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Antigenic structure

Serotyping

antigens

O (lipopolysaccharide)H (flagellar)K (capsular


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Virulence factors

Surface antigen

Somatic antigen

Capsular antigen

Fimbriae

Toxins

Enterotoxins

Hemolysins


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Enterotoxins

Heat labile (LT)

Heat stable (ST)

Vero toxin / Shiga like toxin(SLT)


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Enterotoxin

Heat labile toxin

like choleragen

Adenyl cyclase activated

cyclic AMP secretion water/ions

Heat stable toxin

Guanylate cyclase activated

cyclic GMP

uptake water/ions


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Detection of Heat labile toxin

In vivo methods Ligated rabbit ileal loop method

Infant rabbit bowel

Adult rabbit skin vascular permeability factor In vitro methods

Tissue culture tests

Elongation of CHO cells

Serological tests ELISA Passive haemagglutination test

DNA PROBES


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Detection of Heat stable toxin

In vivo methods Ligated rabbit ileal loop method

Infant rabbit bowel

Infant mouse intragastric test

Serological tests

ELISA

DNA PROBES


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Clinical significance

Most members are opportunistic or causesecondary infections of wounds, theurinary and respiratory tracts, and the

circulatory system Gram-negative sepsis

Urinary tract infections

Meningitis Spontaneous bacterialperitonitis

Diarrhea
http://www.life.umd.edu/classroom/bsci424/Definitions.htmhttp://www.life.umd.edu/classroom/bsci424/Definitions.htmhttp://www.life.umd.edu/classroom/bsci424/Definitions.htmhttp://www.life.umd.edu/classroom/bsci424/Definitions.htmhttp://www.life.umd.edu/classroom/bsci424/Definitions.htmhttp://www.life.umd.edu/classroom/bsci424/Definitions.htm


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most common site of infection by E coli

> 90% of all uncomplicated UTIs

uncomplicated urethritis/cystitis, symptomatic

cystitis, pyelonephritis, acute prostatitis, prostaticabscess, or urosepsis

Pathogenesis

Uropathogenic strains - called P fimbriae or pili,

binds to the P blood group antigen.P fimbriaemediate the attachment of E colito uroepithelialcells.


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patients with intestinal carriage of E colicontaining P fimbriae are at greater risk ofdeveloping UTI

Complicated UTI and pyelonephritis - inelderly patients with structuralabnormalities or obstruction such asprostatic hypertrophy, neurogenicbladders, or in the presence of urinarycatheters


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Diagnosis

Sample collection

Transport

Culture- semiquantitative and quantitativetest

Identification by biochemical reactions

Antibiotic sensitivity


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Diagnosis

Kass concept of significant bacteriuria

Significant 100,000/ ml

Contamination 10000/ ml

Equivocal between 10000 and 100000 - impropersample collection- repeat

Interpretation careful in case

Staphylococcus aureus

Diuretic

Antibiotic intake

Nature of sample


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Screening tests

Griess test

TTC test

Catalase test

M/E gram stained smears

Glucose test paper

Dip slide culture

Antibody coated bacteria test localisationof site of infection


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Diarrhea

EPEC (enteropathogenic)

EAEC (enteroaggregative)

EHEC (enterohemorrhagic) ETEC (enterotoxigenic)

EIEC (enteroinvasive)


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EHEC/ VTEC/ STEC

Mild diarrhea to fatal hemorrhagic colitisand HUS

Primary target- vascular endothelial cells

Prototype strain 0157: H7

first recognized as a cause of illness in1982 during an outbreak of severe bloodydiarrhea; the outbreak was traced tocontaminated hamburger


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EHEC

HUS- acute renal failure,microangiopathichemolytic anaemia, thrombocytopenia

Age groups affected most common in infants,

young children. Major cause of renal failure in childhood

Toxin Verotoxin VT 1 and VT2

VT1- cytotoxin identical to shiga toxin of Shigelladysenteriae

Hemolysins


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EHEC

Diagnosis---

fecal culture

DNA probes

Neutralising antibodies in convalascentpatients reterspectively

Cytotoxic effects on vero or hela cells


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EPEC

Diarrhea in infants and children( infantileenteritis)

Institutional outbreaks or sporadic diarrhea

Identification fresh stool samples blood agarand Mac Conkey agar

Colonies are tested by polyvalent andmultivalent EPEC O antisera

Do not produce toxin or are invasive Adhere to mucosa of small intestine disruption

of enterocyte membrane .


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ETEC

Endemic in tropical countries

Travellers diarrhea- acquired by travellersfrom developed countries when they visit

developing countries. Serotypes O6,O8,O15 etc

Adhesion by fimbriae or CFA 1,2,3,4

Surface attachment is a prerequisite totoxin formation

Forms toxins LT and ST


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Enterotoxigenic E. coli Heat labile toxin

like choleragen

Adenyl cyclase activated

cyclic AMP

secretion water/ions

Heat stable toxin Guanylate cyclase activated

cyclic GMP

uptake water/ions


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EnterotoxigenicE. coli

diarrhea like cholera

milder

travellers diarrhea


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EIEC

Resemble shigella

Non motile, non fermenters of lactose

O antigen cross reacts with shigella

Earlier grouped under Alkalescense dispargroup

Serotypes O112, O124,O28,O136,143,144

Capable of penetrating intestinal epithelial cells Produce an illness similar to shigellosis


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EIEC

Diagnosis

Sereny test in guinea pig

Tissue culture penetration in hela and hep2

cells


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EAEC

Persistent diarrhea in developing world

Stacked brick formation on hep2 cells orglass

Not typed by O antisera

Typed by H antisera

Toxin LMW heat stable toxin EAST 1


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Pyogenic infections

Meningitis new borns mainly

Biliary tract infection

Peritonitis Wound infection

Septicemia fever, hypotension, DIC

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