Lactose fermenting (LF) Non-lactose fermenting (NLF) - PowerPoint Presentation

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Lactose fermenting (LF)

Non-lactose fermenting (NLF)

Gram’s Negative Bacilli

Non enteric bacilli

Enteric bacilli

Late-lactose fermenting (LLF): NLF after 24h, LF after 48h.

E. coli (Escherichia coli)

.

Klebsiella species

.

Enterobacter species.

Citrobacter

Serratia

Others

e.g. Salmonella, Shigella,

proteus,Yersinia

.

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Non lactose fermenting

lactose fermenting

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Family:

Enterobacteriaceae

(ENTERIC BACILLI, COLIFORM).

GENERAL CHARACTERISTICS

* G – ve bacilli or coccobacilli. * Aerobic or Facultative anaerobes.

* Ferment glucose and produce acid + gas.

* Oxidase –ve, catalase +ve * Most of them are normal flora of

human & animal GIT. * Grow well on MacConkey’s agar.

* Transmission either endogenous or person to person

especially in hospital.

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E. coli (Escherichia coli)

Normal flora of human and animal GIT, human female genital tract.

Under electron microscope

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E. coli (Escherichia coli)

There are many

STRAINS SEROTYPED

according to

O

Ag, H Ag, K Ag.

Most strains are Motile, un-capsulated.

Produced dry colonies.

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E. coli (Escherichia coli) infections

DISEASES

INTESTINAL infections

EXTRAINTESTINAL infections

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E. coli (Escherichia coli) infections

INTESTINAL infections

:(caused by some strains)

(e.g. Traveler's diarrhea, dysentery, hemorrhagic infection

).Source of infection either human or animal product.

E. coli

serotypes

Enterotoxigenic

E.coli

(ETEC)

Enteropathogenic

E.coli (EPEC)

Enteroinvasive E.coli (EIEC) Enterohemorrhagic E.coli (EHEC)

Enteroadhesive E. coli (EAEC)

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2) EXTRAINTESTINAL infections

Wound infections, Pneumonia, Bacteremia, Septicemia, UTI .

Its the

common cause of G-ve nosocomial

infection.E. coli (Escherichia coli) infections

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Klebsiella

spp

Klebsiella pneumoniae,

K.oxytoca

, K.ozaenae

Normal flora of GIT.

Non - motile.

Capsulated by large capsule. Mucoid colonies.

Causes

Necrotizing Pneumonia,

Nosocomail infections like UTI

mainly in debilitated patients.

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Laboratory Diagnosis

1

) Specimens

(site of infection e.g. urine, blood, pus…etc).

2) Staining Gram’s stain: Enterobacteriaceae resemble each other morphologically under microscope. So it is difficult to diagnose by microscope.

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Staining

Capsular stain:

Klebsiella stained by this stain, bacilli surrounded by hallo zone.

Laboratory Diagnosis

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Laboratory Diagnosis

3) Culture:

37C°, 24-48h

A) Differential media:

MacConkey’s agar

(selective and differential media):

A.) Lactose fermenter (Pink colonies after 24 hrs.):

E. coli, Klebsiella,

Enterobacter.B.) Late lactose fermenter (Pink after 48 hrs.): Serratia, Citrobacter

. C.) Non – lactose fermenter (Pale colonies after 24 or 48 hrs.): Proteus

, Salmonella

, Shigella.

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MacConkey agar

(selective and differential media)

Bile salt:

Inhibit G-ve other than Enterobacteriaceae

Crystal violet: Inhibit G

+

ve bacteriaNeutral

red: Fermentation indicator Lactose:

Differential between genera Nutrient agar

Laboratory Diagnosis

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Laboratory Diagnosis

E.coli

on MacConkey’s agar

(pink colony due to lactose fermentation

Dry, discreet pink colonies

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Laboratory Diagnosis

Klebsiella

on MacConkey’s agar

(pink mucoid colony due to lactose fermentation

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2) EMB (Eosin Methylene Blue)

contain special dye:

E.coli

 colonies appears green metallic sheen

Others 

no green metallic sheen colonies or colorless.

Laboratory Diagnosis

E.coli

on EMB

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Laboratory Diagnosis

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Laboratory Diagnosis

B) Non differential medium:

Like Blood agar 

Enterobacteriaceae appears (

large, gray, smooth)

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4) Biochemical tests :

1- (

IMViC

) test: used to differentiate between E. coli

and Klebsiella.

I

ndole:- Tryptophan (a.a) Tryptophanase Indole

 add Kovac’s reagent 

red ring (+ve).

M

ethyl red:- Glucose phosphate broth (fer

.)  Acid (

decrease PH)

Methyl red  red

(+ ve), yellow (-ve) Voges

proskauer:- Glucose ph. broth (fermentation) acetyl methyl carbinol 

(5% α – naphthol) + (40% KOH) dark brown (+ve), (-ve) brown-greenC

itrate:

Simmon

Citrate agar(utilize citrate) citrase 

Blue (+ ve),

Green

(- ve). Media contains bromthymol blue indicator.

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4) Biochemical tests :

1- (

IMViC

) test: used to differentiate between

E. coli and Klebsiella

.

Laboratory Diagnosis

Bacteria

I

M

V

C

E. coli

+ (red ring)+ (

red) - (yellow)- (

green) With growthKlebsiella- (colorless ring)

- (yellow)+ (red)

+ (blue)

Without growth

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Laboratory Diagnosis

Indole

test

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Laboratory Diagnosis

Methyl red test

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Laboratory Diagnosis

Voges-proskauer

test

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Laboratory Diagnosis

Citrate test

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4) Biochemical tests :

API 20E system

:( API= analytic profile index)

This become popular for rapid identification

of members of the Enterobacteriaceae and other Gram-negative bacteria.

Plastic strips consist of 20 small wells containing dehydrated media components(consist of 20 tests). Not 100% specific.

Laboratory Diagnosis

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Laboratory Diagnosis

5) Motility test

(at 37C°):

 E.coli causes inverted tree (Christmas tree) due to it’s motility (+ve), while Klebsiella doesn’t as it is not motile (-ve).

Semisolid medium – motility test (inverted Christmas tree

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Thank you