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Wound Culture

Wound Culture


Wound Culture













 When should cultures be performed on chronic wounds? and (2) What is the best method or technique to perform a culture on a chronic wound?


when and how to perform cultures on chronic wounds to guide clinicians in determining the appropriate treatment. [1]

A wound’s microbial balance has been conceptually described by IWII (2016) as a continuum or a gradual increase in the number and virulence of microorganisms and the response those organisms invoke in the host. As the microbial virulence, numbers and pathogenic action increases, the wound infection moves from contamination through colonisation, local infection, spreading infection to systemic infection. Swanson. Therefore, a wound infection must be diagnosed using clinical signs and symptoms, followed by a wound culture that may assist in identifying the causative organisms and resistant species to antibiotics that were commenced. Swanson. 

Evidence indicates that identification of potential chronic wound infection should be considered early using clinical signs such as pain, necrotic tissue, delayed healing, and wound deterioration (in addition to classic signs of infection) to determine the need for collecting a culture (Strength of Recommendation Taxonomy [SORT] level 2); and when a culture is deemed necessary, swab culture using the Levine method is a clinically practical alternative if performed correctly (SORT level 1).[1]

When to collect culture

  • signs and symptoms of infection: See figure 1

  • clinical change in the wound (e.g odor, exudate, rubor, pain, etc): what the patient tells you in the weekly visit is very important, as the other signs/symptoms are subtle
  • wound is stalled or worsened 
  • if you have a patient who is not satisfied, unrealistic expectations, or you have someone who is extremely worried and you are afraid that this might come back to haunt at some point, get a culture unhealthy family/caregiver dynamics : triggered by the items above and as long as the culture is taken in the proper way - see Levine

Types of wound culture

The Levine swab is superior to the Z-swab technique and may be useful for initial wound monitoring, but quantitative biopsies are preferred for evaluation of antibiotic-resistant wounds and to monitor the response to treatment.[2]

  • Punch biopsies: We found moderate quality evidence that punch biopsies provide qualitative and quantitative information about the bacterial load and tissue reaction with nearly 100% sensitivity, 90% specificity and 95% accuracy for predicting wound closure. [2] Biopsies are relatively invasive, costly, require skilled operators, and potentially exacerbate infection. 
  • 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. 
    • Anytime that you do a debridement and bone tissue is removed, it should be cultured
  • 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 aspiration: aspiration samples a limited portion and may enter uninfected tissue and extend infection.[2] This method utilizes a small 22 gauge needle attached to a 10 cc syringe. 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. PIC
  • Wound swabs: swabs are minimally invasive, easier to perform and widely employed in clinical practice, but techniques vary.[2][3] need a CSWD first prior to collecting swab 
    • The Levine technique involves rotating the wound swab over a 1-cm(2) area of the wound [3];
    • the Z technique involves rotating the swab between the fingers in a zigzag fashion across the wound without touching the wound edge[3]
  • In comparative studies, the Levine technique was superior to the Z-swab techniques the Levine technique again detected more organisms in both acute (P≤ 0.001) and chronic wounds (P≤ 0.001).[2] [3], and biopsies were more sensitive for antibiotic-resistant wounds than Levine or Levine-like swabs, suggesting that swabs may be useful for initial wound monitoring, but biopsies are preferred when antibiotic resistance is suspected
  • Molecular methods for microbial identification15: [14]
  • v.      PCR: Is rapid, excellent for excluding common pathogens (such as Pseudomonas and Staphylococcus), can quantitate a sample absolutely (number of organisms per gram) and is inexpensive.  However, PCR is limited in the number of primers that can be utilized and there are different efficiencies in each of those primers (primer bias).  This prevents relative quantification (what percent of each organism compared to the total within the sample).
  • vi.     Sequencing is widely available, takes 5-7 days, identifies bacteria and fungus to the species level, provides a percent of each species for the total sample, thus is relatively quantitative.  The cost is approaching that of culture and sensitivity.  But it only assesses a small amount of the sample, yielding only an answer for a small portion of the wound bed.


Video 1. Levine swab culture technique. Patient with diabetes and chronic ulcer on the left elbow. 

Levine swab culture technique [103]

  • Cleanse the wound with normal saline (do not use antiseptics), pat dry with sterile gauze
  • If excessive debris and/or necrotic tissue are present, may remove them through conservative sharp debridement (if knowledge, skills and license permit)
  • If conservative debridement is performed, cleanse wound bed post debridement with saline and pat dry with sterile gauze
  • Identify the healthiest, cleanest looking area of granulation tissue. Do not choose areas with exudate, pus or devitalized tissue
  • On the identified area, rotate the end of the sterile applicator (swab) over a 1cm2 area. For at least 5 seconds, apply enough pressure  to express fluid from within the wound tissue
  • Insert swab into sterile tube with transport medium and send to lab


After collection of specimen for culture, depending on the patients condition, patients can be started on empiric antibiotic therapy or followed up within 24 hours, or followed up within 3-5 days and then be started on antibiotics based on culture results if clinically indicated. Close monitoring of the patient and wound is important. For instance, if the patient is able to reliably report any complication or worsening of symptoms over a televisit or phone call, an in person follow up appointment may be scheduled in 1 week. If patient has multiple comorbidities or arterial insufficiency, follow up within 24-48 hour may be appropriate. 

The diagnosis of infection is primarily clinical and wound culture is a test to confirm clinical diagnosis. For instance, Video 1 above shows a patient with diabetes, smoker and a chronic ulcer located on the left elbow, near the ulnar nerve. Clinical signs of infection included erythema in the periwound area and a tingling sensation along the distribution of the ulnar nerve, down to the 5th finger. After the wound was cultured, the patient was started on empiric antibiotic therapy with Trimethoprim / Sulfamethoxazole, and asked to return for a follow up appointment in a week. Even though the Levine swab culture technique was followed, the culture of the specimen did not grow any microbes. However, upon follow up the erythema and tingling sensation had subsided. The wound went on to heal with the clinical care - prisma, foam padding, he adhered to treatment plan.  If symptoms had worsened, a punch biopsy for quantitative analysis would have been indicated. In summary, it is important to note that sometimes swab culture results might be negative despite clinical signs of infection. A negative culture result in this case emphasizes the importance of taking the clinical picture into consideration.

pressure ulcer - did padding and prisma and also bactrim/ clinically sound medicine - empiric atb + offloading, recognizing that it was distal neurological symptoms


documentation of the process will raise the e/m level - if level 2, make level 3. if you start atb - elevate MDM

if debridement, culture, start atb - can be separately charged debridement and E/m code 

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