laboratory diagnostic of ctx-m eschericia coli
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CTX-M -
(Detection in
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INTRODUCTION1.E.coli are the most frequently
associated with ESBL.
2.In the Class A ESBLs based on
Ambler Classification.
3.ESBLs are enzmes that mediateresistance to extended-spectrum
(third generation) cephalosporinsand monobactams.
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METHOD
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Antimicrobial SusceptibilityStandard Disc Diffusion Method
1. In-vitro sensitivity testing usingestablished NCCLS (National Committefor Clinical Laboratory Standards)
procedure is carried out with :Ceftazidime (30 g)
Cefotaxime (30 g)
Ceftriaxone (30 g)Aztreonam (30 g)
Cefpodoxime (10 g)
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Antimicrobial SusceptibilityStandard Disc Diffusion Method
2. Zone diameters are read usingthe revised NCCLS document where
any zone within grey zone areconsidered as a probable ESBLproducing strain which requiring
henot ic confirmator testin
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Antimicrobial SusceptibilityStandard Disc Diffusion Method
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Antimicrobial SusceptibilityStandard Disc Diffusion Method
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Double Disk Synergy / DiskApproximation Method
1. This method uses multipletarget disc with clavulanic acid
disc or a single cefpodoximedisc with clavulanic acid disc.
2. Mueller Hinton agar plate is
inoculated with a suspension(0.5 McFarland) made from anovernight agar plate of the test
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Double Disk Synergy / DiskApproximation Method
3. Disc containing the standard, Ceftazidime (30 g)
Ceftriaxone (30 g) Aztreonam (30 g) Cefpodoxime (10 g)
4. Plates are then incubated
overnight at 35C.5. Enhancement of zone inhibition isindicative of presence of an ESBL
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Double Disk Synergy / DiskApproximation Method
ZoneEnhanceme
nt
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Disc Diffusion Method
1. Ceftazidime (30 g) versusceftazidime / clavulanic (30
/ 10 g) and cefotaxime (30g) versus (cefotaxime /clavulanic acid (30 / 10 g)
are placed onto a Muller Hinton agar plate lawnedwith the test organism and
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Disc Diffusion Method
2. Result :
Clavulnic acid
restores activity ofcefotaxime orceftazidime orboth
3. QC :
E.Coli ATCC 25922
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Disc Diffusion Method
2. E-test combination strips,example ceftazidime / ceftazidime clavulanic acid and cefotaxime /
cefotaxime clavulanate areemployed to perform thephenotypic confirmatory testing
3. Strips are inoculated on thesurface of the agar plate andincubated overnight
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Disc Diffusion Method
Ceftaz/CA
Ceftaz
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Others Method
Molecular detection PCR and sequencing
The gold standard
Can detect all variants Easy to perform Labor intensive
Isoelectric focusing (IEF) Automated System
Microscan, Vitek2 & Phoenix