Clinical meaning
Wound infection exists on a continuum from contamination (organisms present but not replicating) to colonization (organisms replicating but not causing harm) to critical colonization (local tissue damage beginning) to infection (organisms invading tissue causing host response). The classic signs of wound infection follow the cardinal signs of inflammation: rubor (redness), calor (warmth), dolor (pain), tumor (swelling), and functio laesa (loss of function). Additional wound-specific infection indicators include purulent drainage, foul odor, increasing wound size, friable granulation tissue that bleeds easily, wound bed discoloration, and delayed healing beyond expected timeframe. Chronic wounds may show subtle signs of infection without systemic responses. Biofilm formation on chronic wound surfaces creates organized bacterial communities resistant to topical and systemic antibiotics. Wound cultures should be obtained using the Levine technique (rotating a swab over 1 cm² of cleansed wound bed with enough pressure to express tissue fluid) rather than swabbing surface exudate, which reflects colonization rather than invasive infection.