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Introduction

Wound infections and abscesses occur as complications of surgery, trauma, or infection that interrupts a skin surface. Material from infected wounds reveals a variety of aerobic and anaerobic microorganisms. Because anaerobic microorganisms are the preponderant microflora in humans and are consistently present in the upper respiratory, GI, and genitourinary tracts, they are also likely to invade other parts of the body to cause severe, and sometimes fatal, infections. Blood cultures should always be drawn from patients with bullous lesions, burn infections, or significant myonecrosis. Infections can also occur when individuals with open wounds are exposed to Vibrio vulnificus, a bacterium present in warm coastal waters. V. vulnificus wound infections are of serious concern in hurricane-affected areas that experience coastal flooding.

Procedure

  1. Procedure for wound culture:

    1. Observe standard precautions.

    2. Most wounds need some form of preparation to reduce the risk for introducing extraneous organisms into the collected specimen. In the presence of moderate to heavy pus or drainage, irrigate the wound with sterile saline solution until all visible debris has been washed away. When culturing chronically present wounds (such as pressure injuries), débride the wound surface of any loose necrotic, sloughed material before culturing. Cultures of the surface alone may be misleading; biopsies of deeper tissue are recommended.

    3. Disinfect the surface of the wound with 70% alcohol or an iodine solution.

    4. Apply sterile gauze pads to absorb excess saline and to expose the culture site. Always culture highly vascular areas of granulation tissue. Wearing sterile gloves, separate margins of deep wounds with thumb and forefinger to permit insertion of the swab deep into the wound cavity. Press and rotate the swab several times over the clean wound surfaces to extract tissue fluid containing the potential pathogen. Avoid touching the swab to intact skin at the wound edges. Whenever possible, submit tissue or an aspirate of the pus.

    5. Immediately place the swab into the appropriate transport container.

  2. Procedure for anaerobic collection of aspirated material:

    1. Decontaminate the culture site with surgical soap and 70% ethyl or isopropyl alcohol.

    2. Aspirate at least 1 mL of fluid using a sterile 3-mL syringe and a needle of appropriate gauge. Immediately transfer the aspirate to an anaerobic transport medium.

    3. Aspiration cultures are commonly done for closed wounds, such as soft tissue abscesses, cellulitis, or infected skin flaps. Tissue biopsies are more often performed during surgery, when infected tissue is more easily accessible.

    4. Never submit a swab when a tissue sample can be obtained.

Properly label the specimen for the microbiology laboratory with the following information:

  1. Patient identification information

  2. Healthcare provider’s name

  3. Date and time the specimen was collected

  4. Anatomic site or specific source of the specimen

  5. Type of specimen (e.g., granulation tissue, abscess fluid, postsurgical wound)

  6. Examination requested

Clinical Implications

Clinically significant pathogens are likely to be present in the following specimens:

  1. Pus from deep wounds or abscesses, especially if associated with a foul odor

  2. Necrotic tissue or débrided material from suspected gas gangrene (also known as clostridial myonecrosis and myonecrosis) infection

  3. Samples from infections bordering mucous membranes

  4. Postoperative wound drainage

  5. Lower extremity ulcers from patients with diabetes

  6. Decubitus ulcers from older or bedridden patients

Clinical Alert

A microscopic examination of pus and wound exudates can be very helpful in diagnosing a pathogenic organism. Consider the following:
  1. Pus from streptococcal infections is thin and serous.

  2. Pus from staphylococcal infections is gelatinous.

  3. Pus from P. aeruginosa infections is blue-green.

  4. Actinomycosis infections show “sulfur” granules.

  5. Bronze discoloration of the skin and fluid-filled blisters are present in gas gangrene.

Interventions

Pretest Patient Care

  1. Explain purpose of and procedure for wound culture. Assess for and document signs and symptoms of wound infection (redness, inflammation, presence and type of drainage, and fever).

  2. Follow guidelines in Chapter 1 for safe, effective, informed pretest care.

Posttest Patient Care

  1. Review test results; report and record findings. Modify the nursing care plan as needed. Monitor the site of infection. Counsel the patient appropriately about treatment.

  2. Follow guidelines in Chapter 1 for safe, effective, informed posttest care.

Reference Values

Normal

Clinical specimens taken from wounds can harbor any of the following microorganisms. Pathogenicity depends on the quantity of organisms present. Quantitative or semiquantitative reporting of culture results may provide information on the relative importance of the various organisms present in the lesion and also the response of the infection to antibiotic therapy.

Potential pathogens:

  1. Actinomyces spp.

  2. Bacteroides and Fusobacterium spp.

  3. C. perfringens and other species

  4. E. coli

  5. Other Gram-negative enteric bacilli

  6. Mycobacterium marinum

  7. Nocardia spp.

  8. Pseudomonas spp.

  9. S. aureus

  10. Corynebacterium jeikeium

  11. Enterococcus spp.

  12. Streptococci (beta-hemolytic)

  13. Candida spp.

  14. V. vulnificus