Diagnostic markers of wound infection

Abstract

The present invention relates to a method of determining the microbial bioburden in a wound (in particular a diabetic ulcer) in a test subject, the method comprising the step of measuring the level of a cytokine in a wound sample, wherein a cytokine level lower than a reference level indicates a significant microbial bioburden in the wound (or a cytokine level higher than a reference level indicates an insignificant microbial bioburden in the wound). The invention provides methods of diagnosis, prognosis and treatment of wound infection, and devices and kits for use in such methods.

1 . A method of determining the microbial bioburden in a diabetic ulcer in a test subject, the method comprising the step of measuring the level of a cytokine in a diabetic ulcer sample, wherein a measured cytokine level lower than a reference level indicates a significant microbial bioburden in the diabetic ulcer. 
     
     
         2 . A method according to  claim 1 , which comprises comparing the measured level of the cytokine in the ulcer sample to a reference level characteristic of a known microbial bioburden, and wherein a measured cytokine level lower than the reference level indicates a higher microbial bioburden in the ulcer. 
     
     
         3 . A method of identifying an infected diabetic ulcer in a test subject, the method comprising the step of measuring the level of a cytokine in a diabetic ulcer sample, wherein a measured cytokine level lower than a reference level indicates the presence of infection in the diabetic ulcer. 
     
     
         4 . A method according to  claim 3 , which comprises comparing the measured level of the cytokine in the ulcer sample to a reference level characteristic of a non-infected diabetic ulcer, and wherein a measured cytokine level lower than the reference level indicates the presence of infection in the ulcer. 
     
     
         5 . A method according to  claim 1 , wherein the method comprises obtaining diabetic ulcer samples from a test subject at intervals of from about 1 hour to about 24 hours and measuring the level of a cytokine in the samples obtained. 
     
     
         6 . A method according to  claim 1 , wherein the method further comprises measuring the total protein content of the diabetic ulcer sample and normalising the measured level of the cytokine to the total protein content. 
     
     
         7 . A method for the treatment of a diabetic ulcer, comprising the steps of measuring the level of a cytokine in a diabetic ulcer sample, and applying an antimicrobial wound dressing to the ulcer if the measured level of the cytokine is lower than a reference level. 
     
     
         8 . A method for the treatment of a diabetic ulcer, comprising the steps of measuring the level of a cytokine in a diabetic ulcer sample, and applying a non-antimicrobial wound dressing to the ulcer if the measured level of the cytokine is higher than a reference level. 
     
     
         9 . A method according to  7  or  claim 8 , wherein the method comprises obtaining ulcer samples from a test subject at intervals, for example at intervals of from 1 hour to 24 hours, and selecting an antimicrobial or non-antimicrobial wound dressing to treat the ulcer at each interval in response to the measured level of the cytokine. 
     
     
         10 . A method according to  claim 9 , wherein the antimicrobial wound dressing is applied to the ulcer if the level of the cytokine is decreasing over time, and the non-antimicrobial wound dressing is applied to the ulcer if the level of the cytokine is increasing over time. 
     
     
         11 . A method according to  claim 1 , wherein the method is an in vitro method carried out on a diabetic ulcer sample removed from a test subject. 
     
     
         12 . A method according to  claim 1 , wherein the diabetic ulcer sample is a diabetic ulcer fluid sample. 
     
     
         13 . A method according to  claim 1 , wherein the diabetic ulcer sample is a diabetic ulcer tissue sample. 
     
     
         14 . A method according to  claim 1 , wherein the ulcer is a diabetic foot ulcer. 
     
     
         15 . A method according to  claim 1 , wherein the level of the cytokine is determined by an immunoassay. 
     
     
         16 . A method according to  claim 15 , wherein the immunoassay is an enzyme-linked immunosorbant assay (ELISA). 
     
     
         17 . A method according to  claim 1 , wherein the cytokine is selected from the group consisting of interleukin-2 (IL-2), interleukin-4 (IL-4), interleukin-5 (IL-5), interleukin-10 (IL-10), interleukin-12 p40 (IL-12 p40), interleukin-12 p70 (IL-12 ρ70), interleukin-13 (IL-13), interferon-inducible protein 10 (IP-10), interferon gamma (IFN-γ), transforming growth factor-β1 (TGFβ1) and tumour necrosis factor-α (TNF-α). 
     
     
         18 . A method according to  claim 17 , wherein the cytokine is selected from the group consisting of IL-2, IL-5, IL-12 p40, IL-12 p70, IFN-γ, and TGF-β1. 
     
     
         19 . A method according to  claim 17 , wherein the cytokine is selected from the group consisting of IL-2, IL-5, IL-12 p40, and IL-12 p70. 
     
     
         20 . A method according to  claim 1 , which comprises measuring the level of two or more cytokines in a diabetic ulcer sample. 
     
     
         21 . A method according to  claim 20 , wherein the two or more cytokines include two or more cytokines selected from the group consisting of IL-2, IL-5, IL-12 p40, IL-12 p70, IFN-γ, and TGF-β1, for example two or more cytokines selected from the group consisting of IL-2, IL-5, IL-12 p40, and IL-12 p70. 
     
     
         22 . A method according to  claim 1 , which comprises measuring the level of three or more cytokines in a diabetic ulcer sample. 
     
     
         23 . A device for use in the method of any preceding claim, wherein the device comprises a selective binding partner for a cytokine. 
     
     
         24 . A device according to  claim 23 , wherein the selective binding partner is an antibody. 
     
     
         25 . A device according to  claim 23  or  claim 24 , wherein the device further comprises a diabetic ulcer sample disposed on the device. 
     
     
         26 . A kit for use in the method of any of  claims 1 - 22  wherein the kit comprises a device according to  claim 23  or  claim 24  and one or more components selected from the group consisting of (a) a wound sampler for removing a diabetic ulcer sample from a test subject; (b) a chart for interpreting the output of the device; (c) a wash liquid for a diabetic ulcer sample; (d) a pre-treatment solution containing a reagent for pre-treatment of the diabetic ulcer sample; and (e) one or more wound dressings for application to a diabetic ulcer. 
     
     
         27 . A kit according to  claim 26 , wherein the wound sampler is selected from the group consisting of a swab and a biopsy punch. 
     
     
         28 . A kit according to  claim 26  or  claim 27 , wherein the wound dressings comprise an antimicrobial wound dressing. 
     
     
         29 . A kit according to  claim 26  or  claim 27 , wherein the wound dressings comprise a non-antimicrobial wound dressing.