Infection, Bioburden, and Antimicrobial Stewardship
The bioburden continuum
Contamination, then colonization, then critical colonization (local infection), then spreading or systemic infection. Biofilm, a matrix-embedded microbial community, is present in most chronic wounds, resists topical agents, and must be physically disrupted by debridement in addition to antimicrobial therapy.
Recognizing infection
Look for erythema, warmth, swelling, pain, purulent or increased exudate, friable granulation, delayed healing, and new odor. NERDS suggests superficial infection (Nonhealing, Exudate, Red/friable tissue, Debris, Smell); STONEES suggests deep or spreading infection (Size increase, Temperature, Os/probe to bone, New breakdown, Erythema at edges, Exudate, Smell). Fever, leukocytosis, and confusion indicate systemic involvement.
Diagnosis and stewardship
Culture after cleansing; the Levine technique (rotate a swab over 1 cm squared for about 5 seconds) samples better than a superficial swab, and tissue biopsy is the reference standard. Treat systemically only for deep, spreading, or systemic infection. Reserve topical antimicrobials for localized critical colonization and reassess within 2-4 weeks; stop agents that are not helping. Osteomyelitis needs imaging, bone biopsy when feasible, and prolonged systemic therapy.
Common traps
- Calling odor alone an infection; necrotic tissue smells.
- Culturing a colonized wound and treating the result.
- Continuing silver or iodine indefinitely.
- Confusing incontinence-associated dermatitis, contact dermatitis, or venous eczema with cellulitis.
Rule of thumb
Treat the patient, not the swab. A chronic venous ulcer with moderate exudate but no erythema, warmth, or pain gets debridement and an absorbent dressing, not oral antibiotics.