1|Page Wound Infection 2022 Is the wound infected? Contamination/Colonization/Infection Contamination non-replicating organism chronic wounds are contaminated indigenous microflora and/or environment Colonization micro-organisms without host injury (infection) symbiotic relationship- host is benefited by impedance of pathogenic bacteria common flora include: corynebacteria sp., coagulase negative staphylococci, and viridans streptococci presence of these in a wound accelerate healing Infection micro-organisms with host injury (tissue invasion and cell destruction) less common than colonization & contamination Biofilm Biofilm: a structured community of microbes that creates behaviours and defences used to produce unique infections (chronic infection). Biofilms are characterised by significant tolerance to antibiotics and biocides while remaining protected from host immunity 60% of chronic wounds contain biofilm, compared to 6% of acute wounds Treatment strategies should be based on the cycle of biofilm, and aim to prevent attachment, interrupt and to prevent or delay re-formation of biofilm Comparison chart Note: symptoms of infection may be masked in immunocompromised patients 2|Page Wound Infection 2022 Wound Depth and bacteria Wound Cultures: When would you obtain a culture of a patient's wound chronic wound that fails to show signs of healing Disappearance/change in granulation tissue Increase in exudates Presence or change to pain Signs of inflammatory soft tissue response Guide antimicrobial selection *NOT TO DIAGNOSE INFECTION- that is done by clinical exam Can you recognize infection what are the signs? Erythema Local warmth Swelling Purulent drainage Delayed wound healing beyond expectations New or increasing pain Increasing malodor Wound Culture Pointers Irrigate normal saline (not bactericidal) No pus, exudates, eschar or necrotic tissue. Perform superficial debridement if possible (remove contaminates out of wound bed) Aerobic (pink) pre-packaged- most common Anaerobic (glass) pre-packaged- use if no air to wound Dual pack (red/white swabs) white is for cultures (anaerobic and aerobic) o Note: anaerobic are only done when no air present (deep cavity) Irrigation-aspiration technique for culture Irrigate ulcer with saline twice Aspirate 2.5ml of residual fluid for aerobic and anaerobic culture Best practice- Levine method swab culture Cleanse wound with normal saline Remove/debride nonviable tissue Wait 2-5 minutes. If ulcer is dry, moisten swab with sterile normal saline Culture the healthiest looking tissue in the wound bed Do not culture exudate, pus, eschar or heavy fibrous tissue Rotate the end of the sterile alginate-tipped applicator over a 1cm2 area for 5 seconds Apply sufficient pressure to swab to cause tissue fluid to be expressed 3|Page Wound Infection 2022 Interpreting a wound culture Purpose o Identify species of bacteria o Determine bacterial populations sensitivity to range of antibiotics Terms o SENSITIVE: antibiotic inhibited growth and/or killed bacteria o INTERMEDIATE: some bacterial population sensitive to antibiotic-others are genetically immune o RESISTANT: bacteria are growing normally, even with presences of antibiotic MIC-lowest concentration of antimicrobial agent which inhibits growth of microorganism (do not compare drug mic) What's next? Check the patient's current medication o Is it correct (sensitive) based on the bacteria reported on the culture report o Does it need to be changed (resistant) If it needs to be changed you need to use your nursing judgement o Is the patient critical- need to call PCP ASAP to change meds (yes even at night) o Can this wait until morning (intermediate susceptibility) o Is the patient stable- can wait until day shift or provider arrives You may need to consult other nurses for their opinions Remember-patient's safety is your main concern
