Microbiological aspects of sepsis

Capt Mohammed Ashraf AliMD (Microbiology)

Outline of Presentation

• Samples

–Collection And Transport

–Processing of sample

• Biomarkers Of Sepsis

• Molecular Based Techniques

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Clinical suspicion of SEPSIS

Foci of infection

Present Not known

BLOOD CULTURE• Grams staining• Culture of sample

from the foci+

• Blood culture

Choice of sample

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Blood Culture

VolumeBefore

antibiotic initiation

Disinfect1 Aerobic

1 Anaerobic

Key points

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Volume of blood• 1:5 ratio - blood to broth• < 10 years : 1 ml of blood for

every year of life• > 10 years: 20 ml

Disinfection• 2% Chlorhexidine/70% ethyl

alcohol• 2% Tincture Iodine (except in

children)

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Outline of Presentation

• Samples

–Collection And Transport

–Processing of sample

• Biomarkers Of Sepsis

• Molecular Based Techniques

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Biomarker Candidates• Multiple

• Biomarkers commonly found in the literature– Lactate levels–Pro-calcitonin levels–C-Reactive Protein

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Lactate to Diagnose Sepsis?

• End-product of anaerobic

glycolysis

• Increased in various settings:

– Excessive energy demands

– Tissue hypoperfusion

(shock)

Glycolysis

pyruvate

CoA lactate

ATP generation

Diminished ATP

Cell Death9Md Ashraf Ali

Lactate levels in diagnosis

• Container: Sodium Fluoride (gray cap)

• Volume reqd : 1 mL plasma

• Special Handling:

No tourniquet.

Place on ice immediately.

• Deliver within 15 minutes.

• Analytic Time: 2 hours

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Procalcitonin

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Procalcitonin levels in diagnosis

• Container: Sterile Vaccutainer

• Volume req: 0.5 mL serum

• Analytic Time: 4 hours

• Test Usage:

– Diagnosis and monitoring of sepsis and septic shock

– monitoring response to antibacterial therapy.12

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• Detection limit: 0.05mg/L

• Accurate and reliable detection

• Sensitivity - 84% and specificity – 81%

Is Procalcitonin an Ideal Biomarker?

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Which biomarker and when?

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MOLECULAR BASED TECHNIQUES

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DETECTION OF BACTEREMIA AND FUNGEMIA

• Samples directly taken from patients

• PCR- simultaneous detection of organism along

with resistant genes (oxacillin, vanco,

carbapenems)

• Results – few hours

• Not cost effective

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Summary Test Sample Volume Container

Blood culture Whole blood

10ml Nutrient medium

Lactate assay Plasma 1 ml Sodium Fluoride (gray tube)

Procalcitonin Serum 0.5ml Sterile vaccutainer

C-reactive protein

Serum 0.5ml Sterile vaccutainer

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THANK YOU