Diagnosis and treatment of wound infection with procalcitonin as diagnostic marker

Abstract

A method of diagnosis or prediction of infection of a mammalian wound, said method comprising the step of detecting the presence of a cytokine selected from the group comprising procalcitonin, amino procalcitonin (N-ProCT), eotaxin, granulocyte macrophage colony stimulating factor (GM-CSF), interleukins IB monocyte chemotactic protein-1 (MCP-1), macrophage inflammatory protein-1 alpha (MIP-1a), regulated upon activation normal T expressed and secreted (RANTES) in fluid taken from the wound. Also claimed is the device for use in the method.

Claims

1. A method of diagnosis and treatment of a local bacterial infection in a wound of a mammal, the method comprising: obtaining fluid from the wound of the mammal; detecting a procalcitonin level in the fluid from the wound of the mammal that is at least equal to or greater than 0.5 ng/ml by observing an appearance of an indicator on a device, wherein the procalcitonin level of at least equal to or greater than 0.5 ng/ml in the fluid from the wound of the mammal is indicative of the local bacterial infection in the wound, and wherein the device is configured such that the indicator appears in the presence of the procalcitonin level of at least equal to or greater than 0.5 ng/ml in the fluid from the wound and the indicator does not appear in the presence of a procalcitonin level of less than 0.5 ng/ml in the fluid from the wound; and administering local and systemic antimicrobial therapy to the mammal to reduce or eliminate the local bacterial infection in the wound of the mammal in response to detecting the procalcitonin level of at least equal to or greater than 0.5 ng/ml.

2. The method as claimed in claim 1 wherein the detecting is carried out in vitro on the fluid from the wound.

3. The method as claimed in claim 1 further comprising comparing a measured procalcitonin level with a reference procalcitonin level characteristic of a non-infected wound.

4. The method as claimed in claim 1 further comprising diluting the fluid from the wound.

5. The method as claimed in claim 1 wherein the wound is a chronic wound.

6. The method as claimed in claim 5 wherein the chronic wound is selected from the group consisting of a pressure ulcer, a leg ulcer, a trauma wound, a surgical wound and a burn wound.

7. The method as claimed in claim 1 wherein the procalcitonin level of at least equal to or greater than 0.5 ng/ml is detected in the fluid by using a binding partner.

8. A method of diagnosis and treatment of a local bacterial infection in a wound of a subject, the method comprising: obtaining a sample from the subject, wherein the sample comprises fluid taken from the wound; detecting a procalcitonin level in the fluid taken from the wound that is at least equal to or greater than 0.5 ng/ml by observing an appearance of an indicator on a device, wherein the device is configured such that the indicator appears in the presence of the procalcitonin level of at least equal to or greater than 0.5 ng/ml in the fluid from the wound and the indicator does not appear in the presence of a procalcitonin level of less than 0.5 ng/ml in the fluid from the wound, and wherein the device includes a first reference band indicative of a first procalcitonin level that is less 0.5 ng/ml, a second reference band indicative of a second procalcitonin level that is greater than or equal to 0.5 ng/ml, a third reference band indicative of a third procalcitonin level that is equal to or greater than 2.0 ng/ml, and a fourth reference band indicative of a fourth procalcitonin level that is equal to or greater than 10.0 ng/ml; diagnosing the local bacterial infection in the wound in response to detecting the procalcitonin level of at least equal to or greater than 0.5 ng/ml; and administering a local and systemic antimicrobial therapy to the subject in response to diagnosing the local bacteria infection in the wound.

9. The method of claim 8, wherein the device includes a pipette, a lateral flow test strip, and a color scale.

10. The method of claim 8, wherein the device includes a test strip in the form of a dip stick and a color scale.

11. The method of claim 8, wherein obtaining the sample includes obtaining 200 microliters of fluid taken from the wound.

12. The method of claim 11, further comprising applying the 200 microliters of fluid taken from the wound onto the device.

13. The method of claim 12, wherein detecting the procalcitonin level of at least equal to or greater than 0.5 ng/ml in the fluid from the wound includes detecting the procalcitonin level of at least equal to or greater than 0.5 ng/ml in the fluid from the wound subsequent to applying the 200 microliters of fluid taken from the wound onto the device.

14. The method of claim 12, wherein applying the 200 microliters of fluid taken from the wound onto the device includes incubating the 200 microliters of fluid taken from the wound at room temperature for 30 minutes.

15. The method of claim 8, wherein the fluid taken from the wound is substantially devoid of blood or tissue plasma remote from a site of the wound.

16. A method of diagnosis and treatment of a local bacterial infection in a wound of a subject, the method comprising: applying a device to the wound that includes a binding partner to bind with procalcitonin present in fluid from the wound; obtaining a sample from the subject by the device, wherein the sample comprises fluid from the wound that is substantially devoid of blood or tissue plasma remote from a site of the wound; detecting a procalcitonin level in the fluid taken from the wound that is at least equal to or greater than 0.5 ng/ml by observing an appearance of an indicator on the device, wherein the device is configured such that the indicator appears in the presence of the procalcitonin level of at least equal to or greater than 0.5 ng/ml in the fluid from the wound and the indicator does not appear in the presence of a procalcitonin level less than 0.5 ng/ml in the fluid from the wound, and wherein the device includes a first color marker indicative of a first procalcitonin level that is less 0.5 ng/ml, a second color marker indicative of a second procalcitonin level that is greater than or equal to 0.5 ng/ml, a third color marker indicative of a third procalcitonin level that is equal to or greater than 2.0 ng/ml, and a fourth color marker indicative of a fourth procalcitonin level that is equal to or greater than 10.0 ng/ml; diagnosing the local bacterial infection in the wound in response to detecting the procalcitonin level of at least equal to or greater than 0.5 ng/ml; and administering a local and systemic antimicrobial therapy to the subject in response to diagnosing the local bacteria infection in the wound.

17. The method of claim 16, wherein the device is a wound dressing.

18. The method of claim 16, wherein obtaining the sample from the subject by the device includes absorbing 200 microliters of fluid from the wound by the device.

19. The method of claim 16, wherein diagnosing the local bacterial infection in the wound includes detecting one of the second, third, and fourth color markers of the device.

20. The method of claim 19, wherein diagnosing the local bacterial infection in the wound includes detecting one of the third and fourth color markers of the device.

Description

EXAMPLE 1

(1) A sample of wound fluid was taken from a wound located on the lower hind limb of a horse. The wound fluid was tested using BRAHMS PCT Q kit which comprises a pipette, a lateral flow test strip and a colour scale and can indicate the presence and level of procalcitonin in the wound fluid. The test consisted of the application of 200 l of wound fluid onto the test area of the strip. The formation of an antibody-procalcitonin complex sandwich on the test strip generated a visible red band on the strip, the intensity of which was used to determine the level of procalcitonin using a semi-quantitative colour scale. The band indicated that the wound fluid contained procalcitonin in the region of 0.5 and 2 ng/ml. Using the test kit guidelines, the level of procalcitonin indicated that bacterial infection was highly likely and therefore local and systemic antimicrobial therapy was administered.

EXAMPLE 2

(2) Twenty eight client-owned horses admitted to the Philip Leverhulme Large Animal Hospital at Leahurst, University of Liverpool, Wirral for either chronic or acute wound treatment were evaluated. The horses ranged between 1 and 19 years of age and included eleven mares, eleven geldings, four fillies and two colts. The wound exudate samples were collected from trauma, surgical and burn wounds.

(3) Reagent Preparation

(4) Sterile Saline: Saline was prepared at a concentration of 0.9% with distilled water and autoclaved at 121 C.

(5) Normal Equine Serum: Sterile equine serum was obtained from Sigma-Aldrich Ltd (Poole, Dorset). Lot: 26H4612; Expiry date: July 2013. The serum was aliquoted, aseptically and frozen at 20 C. until required.

(6) Methods

(7) Wound exudate collection: Wound exudates were collected during dressing changes and centrifuged for 30 minutes at 2000 rpm in order to remove any blood cells. One set of wound exudates were evaluated immediately. The second set of wound exudates were collected and immediately frozen at 20 C. Frozen samples were thawed for 10 minutes at 37 C. and gently vortexed for 30 seconds before applying to the PCT kit.

(8) Procalcitonin (PCT) analysis: PCT analysis was carried out using the BRAHMS PCT-Q kit. This is a semi-quantitative test and takes approximately 30 minutes to obtain a result. Its reading range is between 0.5 ng/ml and 10 ng/ml, and it can be performed in the laboratory or clinic.

(9) Six drops of wound exudate were pipetted into the concave cavity of the kit (200 l) and incubated at room temperature for 30 minutes. After which, the PCT concentration was determined by comparing the colour intensity of the test band with the colour blocks of the reference card supplied with the kit. If no control band appears on the card the test is considered to be invalid.

(10) Results

(11) Normal horse serum (n=3) and sterile saline 0.9% (n=3) were tested using the PCT-Q test and both gave negative results. Both displayed a negative result with only the positive test band visible.

(12) Fresh wound exudate PCT concentrations in eleven horses with chronic or acute wounds were evaluated (Table 1). Table 1 also includes information on the breed, age, sex, type of wound and signs of infection. The centrifuged exudate was tested immediately after being removed from the wound.

(13) Of the 11 exudate samples tested, five gave a result of <0.5 ng/ml (four of these were trauma wounds and one an open chest wound), three samples gave a negative result and two were not tested due to the wound exudates being too viscous despite being centrifuged. Finally, wound exudate from a burn wound was tested and this gave a PCT result of >2.0 ng/ml.

(14) Seventeen wound exudate samples were tested after being frozen at 20 C. (Table 2). Three of these samples (from acute wounds) revealed a PCT result of <0.5 ng/ml. A further eight acute wound samples displayed a negative result (i.e. no band on the test kit). In addition five cases presented wounds that ranged from a few days to three weeks of age and each of these displayed a result of 0.5 ng/ml PCT but there were no visible signs of clinical infection. Finally, the most recent case was from a trauma hock wound that was clearly infected i.e. there was a lot of pus and the wound had a highly pungent odour. This scored <2.0 ng/ml PCT. As a comparison further wound exudates were collected and frozen at 20 C. The test was carried out as above.

(15) In the twenty eight wound exudates that were sampled 46% were negative (from acute wounds), 29% scored <0.5 ng/ml (early trauma wounds), 18% scored 0.5 ng/ml (trauma wounds of a longer duration) and 7% (i.e. 2/28, of which both wounds showed clinical signs of clinical infection i.e. malodorous, slimy, pus) scored 2.0 ng/ml. The PCT concentrations in horses with chronic or acute wounds were compared as seen in Table 2.

(16) TABLE-US-00001 TABLE 1 Case information and PCT results from wound exudates tested immediately after collection. CLINICAL PCT AGE TYPE OF SIGNS OF RESULT BREED SEX (YRS) WOUND INFECTION ng/ml T. B. Bay Filly 1 Trauma ND <0.5 wound L. hind dorsal, just below the knee3 week old wound Welsh X Colt 2 Trauma ND <0.5 wound Welsh Mare 5 Trauma ND <0.5 wound Hunter Gelding 6 Trauma/wire ND <0.5 Arab Gelding 2 Burn Infected >2.0 inflamed, exuding, very malodourous, slimy Cob Gelding 10 Open chest A lot of pus <0.5 wound draining, no malodour Warmblood Gelding 8 Surgical ND Not wound tested infection Sample too viscous. Thoroughbred Mare 3 Hock wound ND Not euthanized tested due to Sample infection too viscous. Cob Gelding 12 Surgical Pus present Negative wound along the result infection edge of the wound Warmblood Gelding 6 Open Pus present Negative draining along the result wound edge of the wound Thoroughbred Mare 12 Trauma ND Negative wound result ND = not determined.

(17) TABLE-US-00002 TABLE 2 Case information and PCT results from wound exudates tested after collection and being stored at 20 C. CLINICAL PCT AGE TYPE OF SIGNS OF result BREED SEX (YRS) WOUND INFECTION ng/ml TB Bay Filly 1 Trauma Slimy 0.5 wound L. hind malodourous dorsal, just below the knee, 3 week wound TB Gelding 16 Trauma Slimy 0.5 wound heel malodourous bulb 15 days old Unknown Mare 5 Colic case ND 0.5 abdominal wound TB Bay Gelding 4 Trauma ND 0.5 shoulder wound 8-9 days old WBxTB Mare 7 Trauma ND 0.5 wound wire injury to hock TB Mare 6 Trauma ND <0.5 wound TB Gelding 7 Trauma ND <0.5 wound Cob Mare 9 Trauma ND <0.5 wound TB Filly 3 Trauma ND 0 wound fetlock British Warm Mare 5 Trauma ND 0 Blood wound to limb 5 days old TBx Geldng 4 Trauma ND 0 wound Cob Mare 19 Hind fetlock ND 0 trauma wound 24 hours old TB Filly 2 Trauma ND 0 wound fetlock Arab Colt 2 Trauma ND 0 wound TB Gelding 6 Trauma ND 0 wound Anglo Arab Mare 5 Trauma ND 0 wound point of hock TBx Mare 16 Trauma hock Sepsis, pus, >2.0 wound malodourous

(18) These results show that procalcitonin in wound exudate is able to determine infection status in acute and chronic wounds. This can be seen by the correlation between higher exudate PCT levels and signs of infection in a variety of wounds. For example a clear correlation can be seen between a PCT level of >2 and clinical signs of infection. The results also show that freezing the samples does not affect the result from the test.

EXAMPLE 3

(19) Wound fluid samples were collected from human chronic wounds and assessed for evidence of procalcitonin using the PCT-Q kit (BRAHMS, Germany). In most cases, wound fluid samples were diluted (1:5 or 1:10) because the samples were too viscous to measure using the PCT-Q lateral flow system.

(20) In one patient (016), a leg ulcer of 3 years duration was considered to be clinically infected. There was also evidence of biofilm and exudate level was heavy. Procalcitonin detection using the PCT-Q kit indicated a level of >0.5 ng/ml.

(21) A second patient (018) had a leg ulcer of 4 years duration, with heavy exudate level and evidence of biofilm. Procalcitonin detection using the PCT-Q kit indicated a level of 0.5 ng/ml.

(22) A third patient (019) had a pressure ulcer of 5 years duration, with heavy exudate level and evidence of biofilm. Procalcitonin detection using the PCT-Q kit was negative (i.e. <0.5 ng/ml).

(23) A negative control sample using horse serum produced a negative result in the PCT-Q kit (i.e. <0.5 nh/ml).

(24) Data generated from the three clinical cases indicate a potential correlation between procalcitonin level in wound exudate and infection status in chronic wounds.