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Basics in CULTURING OF

WOUND SWABS Dr.T.V.Rao MD

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Why Wound Swabs are Important in

Patient CareWound Swabs are one of the Important Specimens sent to Microbiology Departments for Bacteriological and Fungal isolation and Antimicrobiologial Evaluation. However many basic lacuna in Collection, Laboratory identification and reporting makes the Deficit in Effective care of the Patients and increases the potentials for Morbidity and Mortality

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Events in Infected Wounds

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Obtaining a Specimen

Methods of obtaining a specimen from a wound include wound swabbing, needle aspiration and wound tissue biopsy. Although wound swabbing is the most practical and widely used, it is important to use a technique that produces reliable samples for microbiological analysis.

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Wound Culture Protocols

Soft skin and tissue infections with open or draining lesions (Appearance of) insect/spider bite with necrotizing centre, drainage & erythema

• Abscess - ulcer

• Infected laceration

⇒ Culture wound prior to initiation of antibiotics if signs or symptoms of infection are present. If Culture & Sensitivity is obtained after antibiotics have been started, list the drug on the laboratory C& S request.

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What are guideline to

FollowThe technique usually employed for transferring clinical samples from wounds to microbiology laboratories is the wound swab; however definitive guidelines for this relatively simple procedure have yet to be established. Uncertainty about when swabs should be taken, the correct collection procedure and the appropriate protocols for submitting swabs for investigation have led to a situation where clinicians regularly collect and process unsuitable sample

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Swabs should be collected with

Suspected InfectionSwabs should therefore be collected only when clinical criteria point to a wound infection and before any antimicrobial interventions have been initiated

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Are there are Standard Protocol in Collection of

SpecimensIt should be noted that the best technique for swabbing wounds has not been identified and validated. The following recommendations can be used as a guide and should be used in conjunction with local protocols:

When a swab is indicated, the patient should be given a concise explanation of the need for microbiological investigation and what the procedure involves, for example, that swabs are mainly used to recover species from the surface layers rather than from the deep tissues of a wound.

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Cleaning the contaminating

materials is a priorityBefore a representative sample is collected, any contaminating materials such as slough, necrotic tissue, dried exudate and dressing residue should be removed by cleansing the wound with tap water, sterile saline or debridement

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Appropriate Specimen is Important

Do not culture purulent or necrotic debris or drainage over hard eschar.

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Collecting the Optimal Specimen

Sterile swabs with cotton or rayon tips are usually used. If the wound is moist a swab can be used straight from the packaging - if the wound is dry, then the swab tip should be moistened with sterile saline to increase the chances of recovering organisms from the site . Swabs with a transport medium that incorporates charcoal enhance the survival of fastidious organisms

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Basic care in Collecting the

SpecimenCare should be taken to ensure that the swab only comes into contact with the wound surface.

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Care in When Collecting the Swabs1.Cleanse wound by removing excess debris from wound base with normal saline

2. Thoroughly flush wound with sterile saline.

3. Gently blot excess saline from wound bed with sterile gauze.

4. Remove soiled gloves; apply hand sanitizer.

5. Apply clean gloves

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Practical Approach to Collections of Swabs

The swab should be moved across the wound surface in a zigzag motion , at the same time as being rotated between the fingers . Downward pressure to release fluid from the wound surface has been advocated, but this may be painful for the patient.

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Bigger Wounds Needs Multiple Specimens

A representative area of the wound should be sampled. If the wound is large, it may not be feasible to cover the entire surface, but at least 1cm² should be sampled and material from both the wound bed and wound margin should be collected. If pus is present, the clinician should ensure that a sample is sent to the laboratory.

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Devices and Collection of

Swabs

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Collecting the Swabs

Open sterile culture collection/transport kit containing Amies or Stuarts transport medium and remove swab.

If wound is dry, moisten tip of swab with transport fluid at the bottom of the transport sleeve or sterile preservative-free saline (pink saline fish or saline bullet). If wound is moist (weepy) after cleaning, this might not be necessary.

Without touching swab to surrounding wound edges or skin, rotate tip of swab over a 1cm area of open wound for 5 seconds (preferred method), or rotate the swab while making a zigzag pattern across the wound at 10 points

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Steps in Collection in Specimen

Cleanse intact skin with antiseptic and allow to dry.

Expel all air from a 10mL syringe with a 22 gauge needle prior to aspiration. Insert needle into intact skin and apply suction (aspirate).

Aspirate approximately 0.5mL of wound fluid.

Label syringe (see Swab Culture, above).

. After labelling syringe, place in lab biohazard transport bag and transport to the Laboratory

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Transport the Swabs Promptly

Immediately following collection, the swab should be returned to its container (placed into the transport medium) and accurately labelled

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Label and Promptly Transport

Label culture collection/transport kit with name, birth date, specimen source, date and time of culture.

Place in lab biohazard transport container

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Swabs should be Transported without

delaySwabs must be transferred to the laboratory as quickly as possible and ideally processed within four hours of collection

The laboratory report should list the potential pathogens isolated and the amount of growth observed. The antibiotic susceptibilities of any organisms present in the wound may be included, but whether the isolates are of pathogenic and relevant to the Clinical Details furnished

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Appropriate Culturing Yields Precise Results

Apply sufficient pressure to cause tissue fluid to be expressed. It is the bacteria in the tissue fluid that is desired for culture.

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Clinicians should Support with Information

Any supporting documentation for the laboratory should immediately be completed and a note included in the patient's records. It is important to provide information to the laboratory staff that will aid their use of the standard operating protocol, such as any underlying co-morbidities, the patient's age, on-going treatment and wound location

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Microbiological and Clinical Correlation is

the Best Option Antibiotic susceptibilities of any organisms present in the wound may be included, but whether the isolates are of clinical significance or whether antibiotic therapy is required is a matter of clinical judgement. Spreading cellulitis and clinical infections will require systemic antibiotics.

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Limitation of Swab Techniques

To examine the diagnostic validity of swab techniques, analyses of the accuracy as compared to tissue cultures in identifying microbial load provide insight into the utility of swab techniques used for this purpose. The accuracy of swab specimens based on Levine's technique was significantly higher than those based on Z-technique and approached significance when compared to swabs based on wound exudates

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Programme Created By Dr.T.V.Rao MD for Medical and Paramedical Professionals in

the Developing World

Email

doctortvrao@gmail.com