JIJI TV

10/07/2025

♦️Wound Swab Culture♦️
1. Objective
To isolate and identify bacterial or fungal pathogens from a wound infection site and determine their antibiotic susceptibility, guiding appropriate treatment.
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2. Principle
A sterile swab is used to collect exudate or tissue from the base of the wound. The sample is cultured on appropriate media under aerobic and/or anaerobic conditions. Grown organisms are identified, and antimicrobial susceptibility testing is performed using standard methods.
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3. Materials
• Sterile wound swab with transport medium (e.g., Amies)
• Blood agar, MacConkey agar, Chocolate agar
• Anaerobic media (e.g., CDC anaerobe blood agar, thioglycollate broth)
• Inoculating loop or swab
• Gram staining reagents
• Incubator (aerobic and anaerobic, 35–37°C)
• Mueller-Hinton agar + antibiotic discs
• PPE (gloves, lab coat, mask)
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4. Procedure
A. Specimen Collection
1. Clean the wound surface to remove contaminants.
2. Using a sterile swab, collect specimen from the wound base or exudate.
3. Place the swab in transport medium and send to the lab promptly.
B. Culture
1. Inoculate the sample onto:
o Blood agar (detects hemolytic organisms)
o MacConkey agar (detects Gram-negative organisms)
o Anaerobic media if anaerobes are suspected
2. Incubate at 35–37°C:
o 24 hours for aerobes
o 48–72 hours for anaerobes
C. Identification
1. Observe colony morphology and hemolysis.
2. Perform Gram stain from colonies.
3. Confirm identity via biochemical tests or automated systems.
4. Perform antibiotic susceptibility testing (e.g., Kirby-Bauer).
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5. Result Interpretation
Organism Typical Culture Finding
Staphylococcus aureus Golden-yellow colonies, Gram-positive cocci
Pseudomonas aeruginosa Green pigment, fruity odor, NLF on MacConkey
Streptococcus pyogenes Beta-hemolytic on Blood agar
Anaerobes Growth only in anaerobic conditions

6. Uses
• Diagnose wound infections, including:
o Post-surgical wounds
o Diabetic foot ulcers
o Burn wound infections
• Guide targeted antimicrobial therapy
• Detect multi-drug resistant organisms (e.g., MRSA, Pseudomonas)
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7. Conclusion
Wound swab culture is a critical test for diagnosing and managing wound infections. Proper sample collection and timely processing ensure accurate identification of pathogens and effective treatment decisions.
Credit:
Medical Laboratory Scientists

10/07/2025

02/07/2025

Activated Partial Thromboplastin Time (aPTT or PTT) test
1. Objective
The objective of the aPTT test was to measure the time it took for blood to clot via the intrinsic and common coagulation pathways, helping to detect clotting disorders or monitor anticoagulant therapy.
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2. Principle
The aPTT test measured the time it took for citrated plasma to form a fibrin clot after the addition of an activator (e.g., kaolin), phospholipid, and calcium. It specifically evaluated the activity of factors XII, XI, IX, VIII, X, V, II (prothrombin), and I (fibrinogen).
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3. Materials
• Blood sample collected in a 3.2% sodium citrate tube (light blue top)
• aPTT reagent (activator + phospholipid)
• Calcium chloride (CaCl₂) solution
• Coagulometer or stopwatch and water bath
• Centrifuge
• Pipettes and test tubes
• Gloves and lab timer
Read more test : https://earthofstory1.blogspot.com/2025/07/antibody-screening-identification.html
4. Procedure
1. Blood was collected into a citrate tube and centrifuged to obtain platelet-poor plasma.
2. In a test tube or cuvette, a fixed volume of plasma was mixed with the aPTT reagent.
3. The mixture was incubated at 37°C for a defined period.
4. Calcium chloride was added to initiate clotting.
5. The time taken for a visible clot to form was measured using a coagulometer or stopwatch.
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5. Result (Example)
• Normal Reference Range: 25–35 seconds
• Patient Result: 52 seconds
• Interpretation: Prolonged aPTT — may indicate a clotting factor deficiency, lupus anticoagulant, or heparin therapy.
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6. Uses
• Screened for bleeding disorders (e.g., hemophilia A and B)
• Monitored unfractionated heparin therapy
• Detected inhibitors like lupus anticoagulant
• Evaluated intrinsic coagulation pathway
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7. Conclusion
The aPTT test was a valuable and sensitive tool for evaluating coagulation disorders involving the intrinsic and common pathways, and it played a critical role in monitoring anticoagulant therapy and diagnosing bleeding disorders.
Read more test : https://earthofstory1.blogspot.com/2025/07/antibody-screening-identification.html

23/06/2025