Understanding the most current literature describing stages and signs of wound infection helps clinicians to accurately assess wounds.
“If we allow wounds to become infected then it certainly impedes the healing process,” said Patricia A. Slachta, PhD, RN, APRN, ACNS-BC, CWOCN, co-director of the Wound Care Nurse Education Program at Relias.
With an accurate assessment, wound care clinicians can prevent infection or identify signs of wound infection early and allow the body to heal the wound as quickly as possible, without using antibiotics, according to Slachta, who shared her expertise on how to determine if a wound is infected and needs antibiotic treatment.
What is the Difference Between Acute and Chronic Wounds?
An important distinction to make is whether a wound is acute or chronic, according to Slachta. Acute wounds happen traumatically, can include surgical wounds, and heal in a clear-cut fashion.
“Whereas, in a chronic wound, the ‘cascade of cellular events’ does not occur, and the wound becomes stalled in the inflammatory phase,” she said. “Its presence over time certainly can lead to that wound becoming infected.”
Chronic wounds, or those that have been around for more than four weeks, are generally contaminated and colonized with bacteria. While that alone does not translate to infection, it is a step in that direction.
Wound infection is difficult to diagnose by observation, according to Slachta. But sometimes, there are overt signs and symptoms. Knowing these is key, since even culturing wounds has its limitations. That’s because clinicians culture wounds to see if there is an overgrowth of organisms using swab cultures.
According to Slachta, even those clinicians who use current swabbing techniques (and there are a few described in the literature), still get only the superficial bacteria off the wound.
“If it’s a chronic wound, we know we’re going to get bacteria because it’s already contaminated and colonized,” she said.
An Evolving Continuum of Contamination
The continuum of contamination to infection has evolved in the literature. Clinicians used to refer to wounds as contaminated, colonized, critically colonized, and then local progressing to systemic infection, according to Slachta.
Contamination and colonization of the wound remain current terms for every chronic wound, she explained.
“But instead of saying critically colonized, the term ‘localized infection’ is now used,” said Slachta. “That means the bacteria are beginning to penetrate the tissues but are still just in that wound.”
Localized infection can be treated with topical antimicrobials instead of systemic antibiotics, the use of which may lead to antibiotic resistance.
“We want to try to stay away from antibiotics if the patient doesn’t need antibiotic therapy,” she said.
Mnemonics to Know: NERDS and STONEES
There are two mnemonics, NERDS and STONEES, that can better help assess signs and symptoms of wound infection.
NERDS, which stands for Non-healing, Exudate (or drainage), Red and bleeding surface or granulation tissue, Debris, Smell or unpleasant odor, evaluates the degree of colonization.
STONEES, which stands for Size is bigger, Temperature is increased, Osteomyelitis probe to or exposed bone, New or satellite areas of breakdown, Exudate, Erythema/edema, and Smell, evaluates the wound for clinical signs of infection, according to a paper published June 2019 in the Journal of Wound Care.
The mnemonics help to not only identify infection but also clear up the old ways of thinking, according to Slachta.
For example, wound tissue that is really red and bleeds easily suggests a high bacterial load. Yet many clinicians think red tissue that bleeds easily in a wound is a sign of a healthy, healing wound, she said.
“What it really means is the tissue is ‘friable,’ or easily injured, and it’s not healthy,” Slachta said. “If we were to touch the tissue in a healthy wound bed, even if it’s bright pink or even red, it shouldn’t bleed. Red, friable granulation tissue is a sign of at least some local, potential bacterial invasion of the tissue.”
Bacteria, after all, sits on the wound, invades it, and can result in wound infection if it gets into the deeper tissues.
That’s where STONEES comes in, pointing to increasing wound size, a patient’s elevated temperature, exposed bone (when probing with a Q-tip), new tissue breakdown surrounding the wound, redness, swelling, and increasing exudate, according to Slachta.
“STONEES generally indicates that there is a deeper bacterial invasion of that wound, into the deeper tissues. So, we’re moving into that spreading into systemic infection aspect of the spectrum,” she said.
Enter Biofilm
Bacteria gets caught up in a polysaccharide matrix — a membrane that forms around the bacteria that basically protects the bacteria from topical antimicrobials and some systemic antibiotics. This matrix, called biofilm, is present in nearly all chronic wounds, according to Slachta.
While biofilm impedes healing, it doesn’t mean the wound is infected. Biofilm isn’t visible to the naked eye. “We need to address that biofilm,” Slachta emphasized.
To do that, clinicians cleanse a wound. But just dabbing a wound or pouring water on it does not adequately disrupt biofilm. Rather, wound care clinicians generally use a scalpel or curette to debride the wound and its edges.
“If it is not in one’s scope of practice to use a scalpel or curette, we can take a gauze and gently scrub a wound with antiseptic wound cleanser to disrupt biofilm,” she said.
It’s important to disrupt or get rid of the biofilm before applying the topical antimicrobial — a process called wound bed preparation, according to Slachta.
“Even though we’ve been talking about wound bed prep for over 20 years, there are people who still aren’t practicing that way,” she said.
More About Modern-day Wound Care
A strategy for wound bed preparation that has stood the test of time is TIME, which stands for Tissue management, Inflammation and infection, Moisture balance, and Epithelial edge, according to a Wound Care Education Institute blog.
TIME also incorporates some of the newer ways of thinking about wound care, including the fact that wounds heal faster when they’re moist. “We used to dry out wound beds,” Slachta said.
TIME also emphasizes the need for a wound with healthy edges, which will allow the tissue to close over the wound, according to Slachta.
Next Steps
If a wound culture is done, performing a punch biopsy of the wound tissue can reveal what types of organisms have invaded the tissue, which is important especially if clinicians intend to treat a wound with systemic antibiotics.
The method for doing any biopsy involves first cleaning the wound. That’s counterintuitive to some who think that whatever is under the dressing is what they should be culturing, but it’s not, according to Slachta.
“It’s probably pus and … that’s no help,” she said.
Rather, clinicians need to find out what has invaded the tissues, making it necessary to clean a wound before the punch biopsy or swab culture. For swab cultures, if the cleaned wound has a little bit of exudate, and the clinician can press on the area to get a sample of the exudate onto the swab, all the better, according to Slachta.
Because of the contamination/colonization of chronic wounds, cultures are most effective when the STONEES assessment is positive.
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