Synonym

• Culture & Sensitivity (Wound)
• C&S (Wound)
• Culture/Sensitivity (Wound)

Tubes

• Sterile swabs and/or sterile capped syringe/tube with aerobic and/or anaerobic culture transport container (provided by lab)
• Specimens:
• Swab from wound
• 0.5-1 mL of aspirate, exudate, abscess fluid, or granulation tissue

Additional information

• Collection for aerobic wound culture:
• Cleanse the area around the wound with sterile saline to wash away all the visible debris, pus, and drainage, or debride the wound surface of any loose necrotic, sloughed material in chronically present wounds such as pressure sores
• Apply sterile gauze pads to absorb excess saline and to expose the culture site
• Apply swab to highly vascular areas of granulation tissue or separate margins of deep wounds to permit insertion of the swab deep into the wound cavity; press and rotate the swab gently several times to extract tissue fluid
• Immediately, place the swab into the suitable transport container without touching the swab to intact skin at the wound edges
• Collection for anaerobic wound culture:
• Disinfect the culture site with surgical soap and 70% ethyl/isopropyl alcohol or iodine
• Aspirate at least 1 mL of fluid/material using a sterile 3-mL syringe and a needle, usually from deep closed wounds such as soft tissue abscesses, cellulitis, or infected skin flaps
• Immediately transfer the aspirate to an anaerobic transport medium
• A tissue sample is preferred over a swab specimen for culture
• Keep specimen container upright, and send it to lab within 15 minutes
• Do not freeze the specimen or allow it to dry
• Collection of culture specimens should precede antimicrobial therapy whenever possible

Info

• Wound culture is performed to isolate and identify microorganisms causing wound infection
• Sensitivity testing is used to identify which antibiotics an isolated microorganism is sensitive to and which antibiotics the isolated microorganism is resistant to
• Wound infections and abscesses occur as complications of surgery, trauma, or disease that interrupts a skin surface
• Increasingly, Methicillin Resistant Staphylococcus Aureus (MRSA) is the causative organism in spontaneous abscesses

Clinical

• Culture and sensitivity testing of a wound is indicated in the following conditions:
• To detect and identify the microorganisms responsible for wound infection such as:
• Infected lacerations, wounds, sores or burns
• Injuries such as animal bites, human bites, marine stings or scrapes, cuts, and puncture wounds
• To determine the causative organism in persons presenting with wound redness, warmth, or edema with drainage
• To evaluate and differentiate contamination, colonization, or infection in a wound
• To evaluate effective antimicrobial therapy specific to the identified pathogen
• Common pathogenic organisms detectable on wound culture include:
• Staphylococcus aureus / Methicillin resistant Staphylococcus aureus (MRSA)
• Group A beta-hemolytic Streptococci
• Enterococci (Enterococcus faecalis)
• Pseudomonas aeruginosa
• Proteus sp.
• Klebsiella sp.
• Escherichia coli
• Clostridium perfringens
• Peptostreptococcus
• Bacteroides fragilis
• Fusobacterium sp.
• Prevotella
• Mycobacterium marinum
• Corynebacterium jeikeium
• Actinomyces sp.
• Candida sp.
• Aspergillus
• Nocardia spp
• Normal skin flora that may contaminate wound culture samples include:
• Diphtheroids
• S. epidermidis
• Alpha-hemolytic streptococcus
• Pathogenic microorganisms typically gain access to wounds by various routes such as
• Through direct contact, as in transfer from equipment or from the hands of healthcare personnel
• By airborne dispersal, as microorganisms deposited from the surrounding air
• Self contamination as in physical migration from the patient's skin or gastrointestinal tract
• Factors influencing the development of a wound infection include:
• Virulence (pathogenicity and invasiveness) of the microorganism
• Immunologic status of the person
• Presence of an existing chronic infection
• Time interval between skin preparation and surgery
• Nature of the invasive procedure, especially if involving the bowel
• Extent of tissue loss and/or trauma to tissues during surgery
• Adequacy of wound drainage
• Appropriate wound management measures
• Typical presentations of wound infection include:
• Localized erythema typically with soft tissue swelling
• Localized pain/tenderness
• Localized heat
• Edema
• Clinical symptoms suggesting anaerobic infection:
• Foul smelling discharge
• Infection close to a mucosal surface
• Necrotic tissue, gangrene, pseudomembrane formation
• Gas bubbles in tissue or in discharge
• Endocarditis, where routine blood culture is negative
• Infections associated with malignancy
• Wounds due to human or other animal bites
• Black discoloration of blood containing exudative fluids
• Presence of "sulfur granules" in the discharge (in actinomycosis)
• Other clinical presentations include:
• Abscess
• Adjacent lymph node enlargement
• Discolored and purulent discharge
• Delayed healing
• Discoloration of tissues both within the wound and at the wound margins
• Friable, bleeding granulation tissue of the wound
• Wound breakdown associated with wound pocketing/bridging at base of wound

Additional information

• Factors interfering with test results include:
• Recent antimicrobial therapy
• Improper collection technique
• Contamination of the sample
• Inadequate specimen or not a representative sample
• Improper transport medium
• Allowing specimen to dry
• Refrigeration of the sample
• Delayed delivery of specimen
• Related laboratory tests include:
• Relevant tissue biopsies
• Gram stain
• Complete blood count
• Blood culture
• Serum glucose

Nl Result

A normal result may be listed as:

• Negative
• No growth
• No pathogenic organisms isolated

High Result

A positive wound culture must be clinically correlated to the wound and patient's clinical status. When the specimen is correctly collected and the results are consistent with the patient's clinical status, a positive result indicates infection with the identified organism.

Low Result

A negative wound culture may indicate no infection or may be a false negative result due to multiple factors such as:

• Inadequate specimen collection or handling
• Recent antimicrobial agent use

References

• ARUP Laboratories®. Wound Culture. [Homepage on the internet]©2007. Last accessed on March 8, 2007. Available at URL: http://www.aruplab.com/guides/ug/tests/0060132.jsp
• Berg JO et al. Antibacterial properties of EMLA and lidocaine in wound tissue biopsies for culturing. Wound Repair Regen. 2006 Sep-Oct;14(5):581-5.
• eMedicine from WebMD®. Wound infection. [Homepage on the Internet] ©1996-2006. Last updated on March 9, 2006. Last accessed on March 8, 2007. Available at URL: http://www.emedicine.com/MED/topic2422.htm
• Gardner SE et al. Diagnostic validity of three swab techniques for identifying chronic wound infection. Wound Repair Regen. 2006 Sep-Oct;14(5):548-57.
• Kalita JB et al. Delayed post-operative wound infections due to non-tuberculous Mycobacterium. Indian J Med Res. 2005 Dec;122(6):535-9.
• Kelly F et al. Infection control: validity and reliability in wound swabbing. Br J Nurs. 2003 Sep 11-24;12(16):959-60, 962-4.
• Kingsley A. A proactive approach to wound infection. In: Nursing Standard.April 11;vol15;no30;2001. Last accessed on March 7, 2007. Available at URL: http://www.nursing-standard.co.uk/archives/ns/vol15-30/vol15w30p5058.pdf
• Laboratory Corporation of America. Anaerobic and Aerobic Culture and Gram Stain. [Homepage on the internet]©2007. Last accessed on March 8, 2007. Available at URL: http://www.labcorp.com/datasets/labcorp/html/chapter/mono/mb024900.htm
• LabTestsOnline®. Staph Wound Infections and Methicillin Resistant Staphylococcus aureus. [Homepage on the Internet]© 2001-2006. Last reviewed onJune 3, 2005. Last accessed on March 8, 2007. Available at URL: http://www.labtestsonline.org/understanding/conditions/staph.html