LAST MONTH, I described the critically colonized wound and how to manage it (Wound and Skin Care, "Calling on NERDS for Critically Colonized Wounds").* But suppose that in spite of using a nanocrystalline silver product, you notice increased edema, erythema, and foul-smelling purulent drainage from the wound, which is getting larger. You also notice two smaller satellite lesions. The area around the wound is warm to the touch and, on closer inspection and probing, you reach bone. In this article, I'll describe what to do when the bacterial balance tips from colonization to infection.
What causes the balance to tip?
Despite therapy based on best wound care practices, some wounds still become infected. Patient factors predisposing a wound to infection include inadequate vascular perfusion, inadequate nutrition, immune system disorders, chronic diseases such as diabetes, prior surgery or radiotherapy, drug and alcohol use, or smoking. Local host factors such as the size of the wound and the presence of foreign bodies also can tip the balance.1-3
The virulence and number of microbes may also help push a wound from colonization to infection, although these factors may be less important than host factors.2
Recognizing wound infection
An infected wound also may have signs of critical colonization. Use the mnemonic STONES to help you remember the factors associated with a deep compartment wound infection:1
Size of the wound is increased (not by ischemia or pressure)
Temperature of surrounding wound area is increased. A temperature difference of 3[degrees] F (1.7[degrees] C) between two mirror image sites should make you suspect an infection.1
Osteomyelitis; that is, you can probe to the bone
New areas of breakdown, such as satellite lesions
Exudate, erythema, and edema are present. A wound infection triggers an inflammatory response.
Smell or odor is coming from the wound, distinct from the smell of exudate mixed with wound dressing material. If wound odor is still present after wound cleaning, suspect a bacterial cause. Gram-negative and anaerobic bacteria can create foul odors due to tissue breakdown. Many bacteria have a distinct odor such as the sweet odor that characterizes Pseudomonas or the ammonia-like odor of Proteus.
Unexpected pain/tenderness (particularly in a neuropathic limb) and pocketing or bridging at the base of a wound also indicate wound infection.4 The patient also may have systemic signs of sepsis, such as hypotension, fever, chills, and organ failure, requiring parenteral antibiotics.1
What to do
Start by obtaining a good sample for culturing, using the Levine method: Rotate a cotton-tipped swab over a 1 cm2 area of the wound with enough pressure to express tissue fluid.5 Remember that culture results are only part of the picture-also perform a thorough clinical assessment to accurately assess a wound infection.
The culture usually helps identify the causative microbes. Gram-positive microbes are the culprit in most infected wounds of less than 4 weeks duration. Wounds that have been infected more than 4 weeks tend to be polymicrobial in nature, making it harder to identify and eradicate the causative agent. Aerobic bacteria (such as Escherichia coli) use up oxygen, creating tissue hypoxia that paves the way for infection with anaerobes (such as Bacteroides fragilis).2
You'll also need to consider the virulence of the microbe. For example, beta-hemolytic Streptococci can cause severe wound infections at very low numbers.2
Administer systemic antibiotics as prescribed to treat deep compartment infections. Many clinicians continue to use topical antimicrobials, particularly in high-risk patients such as those with immune deficiency or peripheral vascular disease.
Reassess the treatment plan at weeks one, two, and four.1 A 20% to 40% reduction in wound size at weeks two and four may indicate bacterial balance has been achieved.6
If the wound doesn't heal despite optimum antimicrobial therapy, other factors may be involved, such as ischemia, continued pressure, antibiotic-resistant organisms, poor nutrition, or poor glycemic control.