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How to Culture a Wound

I see it all of the time. Wound care clinicians performing wound cultures incorrectly, or obtaining cultures just because there is an open wound. With this being said, there are certain health care settings where per protocol, swab cultures are taken on every wound, even without signs and symptoms of infection. But I want you to always ask yourself a few questions when determining if a culture is warranted: Are there signs and symptoms of infection? Is there an odor after the wound has been cleansed? Has wound healing stalled? Maybe there is a biofilm present?

Local Signs and Symptoms of Wound Infection

Every wound has the potential for infection, but it is important to differentiate between infection and colonization. Wound care specialists have developed somewhat of a "trained eye", but there is no text edition that provides color photos of every wound with bioburden. Infection may be present if any of the following are present in the wound area:

  • Erythema, warm to touch
  • Edema, Induration
  • Increased pain, tenderness
  • Increased exudate
  • Friable granulation tissue
  • Odor "after" wound cleansing

Most Common Pathogens Found in Wounds

  • Aeromonas
  • Bacteroides
  • Candida
  • Clostridium
  • Enterobacter
  • Enterococci
  • Escherichia coli
  • Fusobacterium
  • Klebsiella
  • Peptostreptococcus
  • Proteus
  • Pseudomonas
  • Staphylococcus aureus
  • Streptococcus

Types of Wound Cultures

Swab culture: A swab culture is the most common technique used because it is non-invasive, and most cost-effective. This type of culture will usually identify the bacterial species of the infection, and help steer antibiotic therapy. Surface swabs will only unveil the colonizing organism, and may not reflect deeper tissue infection. An acceptable alternative to quantitative tissue culture is the Levine quantitative swab technique:

The Levine Quantitative Swab Technique:

  1. Cleanse wound with normal saline.
  2. Pat dry wound bed with sterile gauze.
  3. Culture the healthiest looking tissue, excluding exudate, purulent, devitalized tissue.
  4. Spin the end of the sterile applicator over a 1cmx1cm area for at least 5 seconds.
  5. Apply sufficient pressure to swab, causing tissue fluid to be expressed.

Deep-tissue biopsy: A deep-tissue or punch biopsy for a quantitative culture is the gold standard for identifying wound bioburden and diagnosing infection. Biopsies are invasive, painful, expensive, and not always available in all settings. Biopsies must be performed by qualified and trained providers, who aren’t always available.
Providers most frequently use a disposable special circular blade punch tool to remove a plug of deeper layers of skin for testing. Depending on the size, stitches may be necessary to close the wound.

Needle culture: Needle aspiration is a less invasive technique to use in wounds such as puncture wounds. This method includes inserting a small 22 gauge needle. In order to obtain a sample of the fluid to be biopsied, the clinician pulls back on the plunger and then changes the angle of the needle two or three times to remove fluid from different areas of the wound.

Careful assessment and documentation of the patient and the wound will help clinicians determine when to perform a wound culture for pathogens, and the best technique for gaining the culture sample. Protocol may vary depending on health care setting, so be sure to follow your facility guidelines.

Agency for Healthcare Research and Quality AHRQ clinical practice guidelines, Pressure Ulcers in Adults: Prediction and Prevention and Treatment of Pressure Ulcers
CMS: Guidance to Surveyors for Long Term Care: Regulation F272 (Comprehensive Assessment), F279 (Comprehensive Care Plans), F280 (Comprehensive Care Plan Revision), F281 (Services Provided Meet Professional Standards, F309 (Quality of Care), and F314 (Pressure Sores), and related requirements under F157 (Notification of Changes), F353 (Sufficient Staff), F385 (Physician Supervision), and F501 (Medical Director) (CMS, Guidance to Surveyors for Long Term Care Facilities. August 17, 2007)
Levine NS, Lindberg RB, Mason AD, Pruitt BA Jr. The quantitative swab culture and smear: a quick, simple method for determining the number of viable aerobic bacteria in open wounds. J Trauma. 1976;16(2):89-94.
Zuber TJ. Punch Biopsy of the Skin. Am Fam Physician. 2002 Mar 15;65(6):1155-8.

About the Author
Cheryl Carver is an independent wound educator and consultant. Carver's experience includes over a decade of hospital wound care and hyperbaric medicine. Carver single-handedly developed a comprehensive educational training manual for onboarding physicians and is the star of disease-specific educational video sessions accessible to employee providers and colleagues. Carver educates onboarding providers, in addition to bedside nurses in the numerous nursing homes across the country. Carver serves as a wound care certification committee member for the National Alliance of Wound Care and Ostomy, and is a board member of the Undersea Hyperbaric Medical Society Mid-West Chapter.

The views and opinions expressed in this blog are solely those of the author, and do not represent the views of WoundSource, HMP Global, its affiliates, or subsidiary companies.