screening for resistant organisms

7/28/2019 Screening for Resistant Organisms

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Screening for Resistant

Organisms

Dr Koh Tse Hsien

Singapore General Hospital


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How do you detect resistant

organisms?

Passive surveillance Normal lab results

No extra work or cost

May only pick up tip of the iceberg (20%)

Active surveillance Screening

Picks up colonization

Extra work and cost


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Why screen?

There is a problem

resistant bacteria affects patient morbidity and

mortality

infections with resistant bacteria increase costs

There is an intervention

isolation of patient

clearance of carriage

empirical treatment


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What to screen

Vancomycin-resistant Enterococcus (VRE)

Methicillin-resistant Staphylococcus aureus

(MRSA)

Extended-spectrum cephalosporin resistant

Enterobacteriaceae

Carbapenemase-producingEnterobacteriaceae (CPE)

etc..


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Selective agars

Antibiotic content allows selection of

resistance phenotype

Chromogenic indicator may allow presumptive

identification

Takes at least 24 hours

Enrichment broth step? Labor intensive

Allows isolation of strain for typing studies


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PCR

May be more sensitive

Faster time to result

May be technically complex Expensive


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http://www.google.com.sg/url?sa=i&rct=j&q=&esrc=s&frm=1&source=images&cd=&cad=rja&docid=T1nShUv53zAIFM&tbnid=xnyGPlAG2NXJkM:&ved=0CAUQjRw&url=http://www.bio-rad.com/en-se/product/mrsaselect-medium&ei=ALEqUs-cKMWIrQfY04CoDw&bvm=bv.51773540,d.bmk&psig=AFQjCNHmtvx2My8tG3QZxn8uktnG2f09HA&ust=1378615881198045http://www.google.com.sg/url?sa=i&rct=j&q=&esrc=s&frm=1&source=images&cd=&cad=rja&docid=T1nShUv53zAIFM&tbnid=xnyGPlAG2NXJkM:&ved=0CAUQjRw&url=http://www.bio-rad.com/en-se/product/mrsaselect-medium&ei=ALEqUs-cKMWIrQfY04CoDw&bvm=bv.51773540,d.bmk&psig=AFQjCNHmtvx2My8tG3QZxn8uktnG2f09HA&ust=1378615881198045


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MRSA

Pooled nose, axilla, (throat), and perinealswab

http://www.bd.com/ds/productCenter/215084.asp

http://www.bio-rad.com/
http://www.google.com.sg/url?sa=i&rct=j&q=&esrc=s&frm=1&source=images&cd=&cad=rja&docid=T1nShUv53zAIFM&tbnid=xnyGPlAG2NXJkM:&ved=0CAUQjRw&url=http://www.bio-rad.com/en-se/product/mrsaselect-medium&ei=ALEqUs-cKMWIrQfY04CoDw&bvm=bv.51773540,d.bmk&psig=AFQjCNHmtvx2My8tG3QZxn8uktnG2f09HA&ust=1378615881198045http://www.google.com.sg/url?sa=i&rct=j&q=&esrc=s&frm=1&source=images&cd=&cad=rja&docid=T1nShUv53zAIFM&tbnid=xnyGPlAG2NXJkM:&ved=0CAUQjRw&url=http://www.bio-rad.com/en-se/product/mrsaselect-medium&ei=ALEqUs-cKMWIrQfY04CoDw&bvm=bv.51773540,d.bmk&psig=AFQjCNHmtvx2My8tG3QZxn8uktnG2f09HA&ust=1378615881198045


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Enrichment or no enrichment?

Adding MRSA broth (ThermoScientific)

increased detection by 50% in SGH samples

But adds one extra days incubation to confirm

positive

http://www.rapidmicrobiology.com/news/603h120p.JPG


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PCR

http://www.bd.com/geneohm/english/products/max/instrument/

http://www.cepheid.com/tests-and-reagents/clinical-ivd-test/xpert-mrsa

http://www.roche.com/products/product-details.htm?type=product&id=109


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http://www.cepheidondemand.com/Summer-2011/cover-story.php


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David, M. Z. et al. 2010. Clin. Microbiol. Rev. 23(3):616-687

FIG. 2. Hypothetical virulence factors in USA300 and other CA-MRSA strains


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VRE

Stool or rectal swab


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Vitek II


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Magnapure

Qiagen DNA minikit


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CPE

Stool or rectal swab


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5ml TSB+Meropenem disk

Meropenem 10 g

disk


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MacConkey Agar with Imipenem DiskImipenem


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Chromagar KPC


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ChromID ESBL

Cefpodoxime


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MAST Adatabs


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MacConkey +Meropenem 1 mg/L


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ChromID CARBA


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Direct from stool


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Questions to ask yourself before

starting surveillance What is the target population?

Which resistant organisms do you want to

identify?

Which method? What body sites to sample?

How long are you going to survey?

Admission surveillance or periodic surveillance? Who pays?

Is there will and money to intervene?

screening for resistant organisms

Documents