Diagnosing wound infection - a clinical challenge

Transcription

1 Diagnosing wound infection - a clinical challenge Keith F Cutting Merimbula, 5 th November 2010

2 Wound infection microbial load immune system microbial load immune system infection host response

3 Diagnosing wound infection Is it an established skill? Controversy! Lack of evidence? Poor interpretation of evidence?

4 Wound infection a major cause of patient morbidity But detection rates are dependent on criteria used Epidemiology and infection value?

5 Identifying infection? Microbiological Clinical

6 But microbiology can only provide info on species present and antibiotic sensitivity. What about virulence?

7 Methods of microbiological sampling superficial wound swab deep tissue biopsy provides an overview of the surface microbiology (semi-quantitative and quantitative assay) samples a specific area of the wound (quantitative assay)

8 Issues Deep tissue biopsy is highly selective. Quantitative culture may miss superficial bacteria that can adversely effect healing. Wound contamination generally occurs from the surface. Deep wound organisms possibly disseminate from superficial isolates.

9 Problems with wound swabbing we don t know how to do it high incidence false +ve, false-ve viable but non-culturable bacteria the presence of pathogens does not always correlate with infection

10 S. aureus present in 88% of non-infected leg ulcers (n=58) (Hansson, 1995) S. aureus present in 43% of infected leg ulcers (n=44) and 53% of non-infected leg ulcers (n=30) (Bowler, 1999)

11 The eradication of bacteria does not correlate with healing 47 vlu patients 50% local treatment (bandage) 50% above + systemic antibiotics Results no difference in healing rates Alinovi et al 1986 Journal of the American Academy of Dermatology. 15(2 Pt 1):186-91

12 Issues Correct technique for surface sampling? Cleanse wound surface before sampling? Superficial swab does not reflect deep wound bacteriology Discontinue antimicrobials before sampling?

13 Wounds should only be sampled when: Clinically infected No clinical signs of infection but deteriorating Long history of failure (chronic wounds) A surface sample may then provide data on: Presence of potential pathogens Diversity of microorganisms Indication of synergy Bowler, Duerden, Armstrong, 2001

14 Should we differentiate between acute and chronic wound infection?

15 The signs of wound infection remain rooted in Celsus observation of 2000 years ago - the classical signs of inflammation: Rubor - redness Tumor - swelling Calor - heat Dolor - pain Celsus 30 B.C. 45 A.D.

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17 Acute wound infections. Their natural history is one of rapid manifestation, prompt tissue destruction and then resolution. Usually resolve within days following systemic antibiotics

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21 Traditional Abscess Cellulitis Discharge Serous exudate / inflammation Seropurulent Haemopurulent Pus Additional Delayed healing Discolouration Friable granulation tissue/bleeds easily Pain/tenderness Pocketing Bridging Malodour Wound breakdown Cutting & Harding 1994 Journal of Wound Care 3(4):

22 1. Acute/surgical wounds (primary & secondary) 2. Arterial ulcers 3. Burns (partial & full thickness) 4. Diabetic foot ulcers 5. Pressure ulcers 6. Venous leg ulcers Cutting et al 2005

23 Wound infection continuum Sterile Contaminated Colonized Critically colonized Infected increasing bioburden irrelevant demarcation lines? clinical relevance? Kingsley 2001

24 Critical Colonisation what is it? silent infection covert infection refractory sub-clinical infection indolent occult infection recalcitrant

25 delayed healing pain/tenderness increased serous exudate change in colour of the wound bed friable granulation tissue absent/abnormal granulation tissue abnormal odour. Septicaemia Invasive infection Local inf/crit Colon Colonisation Contamination Edwards & Harding 2004 equates CC with clinical signs of local infection.

26 The inability of the wound to maintain a balance between the increasing bioburden and an effective immune system the wound has become compromised, but is not yet demonstrating overt clinical signs of infection other than non-healing. Cutting 2003

27 Bacteria and wounds Micro-organisms in a chronic wound need to be evaluated as a collective ecosystem rather than as individual species

28 Bioburden - metabolic load imposed by microorganisms Colonised Infected sub clinical clinical suppressed immune response K.F.Cutting species, synergy biofilm (climax community, polymicrobial Local inf Classical signs Rubor Tumor Calor Dolor Local inf Subtle signs (Cutting & Harding 1994, Cutting et al 2005) Spreading inf e.g. acute cellulitis bacteraemia, septicaemia

29 Emergence of tissue viability often community-based provided by a wide range of clinicians Nursing to provide leadership in the quest for clarity in respect of developing a universally accepted (accurate) diagnosis for wound infection?