Effect of a New Purified Collagen Matrix With Polyhexamethylene Biguanide on Recalcitrant Wounds of Various Etiologies: A Case Series

Introduction. The management of chronic, nonhealing wounds in patients with multiple comorbidities continues to be a challenge for health care practitioners. Chronic wounds typically do not progress through the normal phases of wound healing and generally remain stagnant during the inflammatory phase, resulting in an increase in proteolytic enzymes with degradation of the extracellular matrix. Bacterial biofilm has been documented to be one of the main factors delaying wound healing, resulting in the prolongation of the inflammatory phase. Objective. In order to control biofilm formation, sequester proteolytic enzymes, and provide a biocompatible scaffold to support healing, the investigators utilize a purified collagen matrix containing polyhexamethylene biguanide (PCMP) in a case series of 9 wounds on 8 patients with multiple comorbidities who did not respond to previous conventional or adjuvant therapy. Materials and Methods. Wound etiologies included 3 pressure ulcers, 1 diabetic foot ulcer, 1 venous leg ulcer, 2 postsurgical wound dehiscences, 1 ulcer secondary to calciphylaxis, and 1 traumatic wound secondary to hematoma. The average wound size at the first PCMP application was 34.0 cm², and the wounds were present for an average of 9.2 weeks prior to the first PCMP application. Results. Patients received an average of 5.8 PCMP applications. Of the 6 wounds that healed, average time to closure from the first PCMP application was 10 weeks. The remaining 3 wounds demonstrated improved wound appearance with 100% granulation tissue and an average area reduction during PCMP treatment of 61.4%. Conclusions. This case series demonstrated that PCMP along with good wound care supported both wound closure and improvements in wound bed condition and area reduction on recalcitrant, nonhealing wounds of various etiologies. 

Chronic, nonhealing wounds in patients with multiple comorbidities continue to be a challenge for health care practitioners to manage and are an increasing burden on health care systems worldwide. Indeed, chronic wounds are estimated to affect up to 1% of the Western population; up to 4.5 million people in the United States alone experience chronic lower extremity ulcers.^1,2 By definition, chronic wounds are wounds that fail to proceed through the normal phases of wound healing in an orderly and timely manner. Chronic leg and foot ulcers have been found to last an average of 12 to 13 months and recur in more than half of patients.¹ The impact of chronic wounds can be staggering, leading to significant loss of function, reduced quality of life, and substantial morbidity and even mortality. In fact, 5-year mortality rates due to lower extremity complications of diabetes are similar to or exceed many types of cancers, including those from prostate cancer, breast cancer, and Hodgkin’s disease.³

Chronic wounds fail to proceed through the normal phases of wound healing (ie, hemostasis, inflammation, proliferation, and remodeling), typically stalling in the inflammatory phase.^1,4,5 The chronic wound environment is characterized by excessive and persistent levels of proinflammatory cytokines, leading to elevated levels of proteases that degrade the extracellular matrix and prolong the inflammatory phase.^1,5-7 This hyperinflammatory, proteolytic environment prevents the wound from progressing into the proliferative phase, resulting in stalled reepithelialization and the formation of defective granulation tissue.^2,6

Excessive wound bioburden is recognized as an important factor in delaying wound healing.⁴ In contrast to planktonic, or free-floating, bacteria, microbes in the chronic wound bed are believed to exist mainly in biofilm communities, which attach to the wound surface and exist in microcolonies enclosed in a protective matrix of polysaccharide material.^8-10 Biofilms differ genotypically and phenotypically from planktonic bacteria, resulting in higher tolerance to antibiotics and to the host immune response.^8,9,11,12 Biofilms have been increasingly implicated in playing a key role in perpetuating the chronic, nonhealing wound environment.^4,8,11,13-15

Indeed, biofilms have been estimated to be present in nearly 80% of all human infections¹⁶ and have been detected in 60% of chronic wounds.¹³ More recently, it has been argued that biofilms exist in all chronic wounds.^4,17,18 

With growing recognition of the role of biofilms in delayed wound healing, the need to effectively manage biofilm in patients with chronic wounds is increasingly appreciated. Debridement is effective at removing biofilm and is an important component of wound management; however, experimental and clinical data indicate biofilm begins to reform within 24 hours after debridement and can fully mature within 3 days.¹⁹ Thus, although beneficial for removing mature biofilms, debridement alone is an insufficient strategy for preventing the reformation of biofilm and promoting healing.²⁰

A purified collagen matrix containing a polyhexamethylene biguanide (PHMB) antimicrobial (PCMP; PuraPly Antimicrobial; Organogenesis Inc, Canton, MA) has been developed to support wound healing. This product consists of 2 layers of predominantly Type I collagen matrix that have been purified to inactivate viruses and remove cells and cellular debris. Importantly, the native structure of the collagen matrix is preserved,^21,22 which has been shown to be an important factor in determining a collagen dressing’s ability to quench proteolytic enzymes that characterize the chronic wound environment.⁷ Further, the matrix is cross-linked and coated with PHMB, enabling it to resist proteolytic degradation and providing a sustained antimicrobial effect. Polyhexamethylene biguanide is an extensively studied antimicrobial with a broad antimicrobial spectrum and no reported cases of antibacterial resistance.^23,24 Unlike some antimicrobials, PHMB is nontoxic to human cells and does not impair the healing process.²⁵ 

The use of PCMP to manage bioburden and support healing in patients with challenging chronic wounds has been described.²⁶ This paper extends this experience to a series of patients with multiple comorbidities and wounds of various etiologies

Clinicians from a single facility retrospectively reviewed the clinical course of 8 patients with a total of 9 wounds who had failed to respond to previous conventional or adjuvant therapy and who were subsequently treated with PCMP. All 8 patients presented to Wayne UNC Health Care’s Wound Healing and Hyperbaric Center (Goldsboro, NC). As depicted in the Table, patients ranged in age from 52 to 79 years and suffered from multiple comorbidities. Wound etiologies included 3 pressure ulcers, 1 diabetic foot ulcer, 1 venous leg ulcer, 2 postsurgical wound dehiscences, 1 ulcer secondary to calciphylaxis, and 1 traumatic wound secondary to hematoma. The PCMP was applied once weekly after debridement wherever applicable after the wound bed was sharply debrided to physically remove excessive bioburden and biofilm. The PCMP was moistened with saline to improve handling characteristics and conformity to the surface of the wound and secured in place with adhesive strips. The product then was covered with a nonadherent primary dressing (ADAPTIC TOUCH Non-Adhering Silicone Dressing; Acelity, San Antonio, TX) and moisture-retentive secondary dressings (AQUACEL; ConvaTec, Bridgewater, NJ) as required. Compression therapy and/or offloading was administered as appropriate. Wounds were assessed weekly and good conventional care was administered concurrently throughout the course of treatment. 

The average wound size at the first PCMP application was 34.0 cm², and the wounds were present for an average of 9.2 weeks prior to the first PCMP application. Patients received an average of 5.8 PCMP applications. Of the 6 wounds that healed, the average time to closure from the first PCMP application was 10 weeks. The remaining 3 wounds demonstrated improved wound appearance with 100% granulation tissue and an average area reduction during PCMP treatment of 61.4%.

Case 1: sacral pressure ulcer 

A 53-year-old blind and bedridden woman with a history of diabetes mellitus, hypertension, and multiple sclerosis presented with an infected Stage 4 sacral pressure ulcer measuring 27.5 cm² with sacral bone exposed, serosanguinous drainage, and hypergranulation at the wound edges. Following positive nuclear bone scan and bone biopsy and cultures for osteomyelitis, intravenous antibiotic therapy and local wound care and offloading were initiated. At week 6, the sacral bone was no longer exposed and the wound presented with granulation tissue. Sharp debridement was performed at week 8 and negative pressure wound therapy (NPWT) was started. At week 22, when a 79% reduction in wound size was observed, PCMP was applied to the wound, which then measured 5.88 cm². After 4 weekly applications, the wound size had reduced to 2.55 cm² and 100% granulation tissue was observed. The patient was lost to further follow-up due to hospitalization.

Case 2: dehisced incision

A 60-year-old man with diabetes mellitus and a history of coronary artery disease, hypertension, and diverticulitis presented post colectomy with a full-thickness, midline abdominal postsurgical wound measuring 91.5 cm² with serosanguinous drainage, undermining, and retention sutures. The patient developed an infection and recurrent fascial dehiscence requiring 2 operative procedures, an application of an acellular collagen matrix, and NPWT. At week 8, NPWT was discontinued, and PCMP was applied to the wound measuring 66.6 cm² and continued for 12 weekly applications. Wound size and appearance gradually improved and, by week 23, fragile epithelium was noted (Figure 1). By week 25, the wound was healed with complete epithelialization, and the patient was discharged from the clinic.   

Case 3: sacral pressure ulcer

A 77-year-old woman with a history of hypertension, dementia, Parkinson’s disease, and lumbar kyphoplasty presented with an infected Stage 4 sacral pressure ulcer measuring 48.75 cm² and was admitted for surgical debridement. The patient was started on NPWT and, at week 4, developed an infection with worsening appearance of the ulcer with sacral bone exposed and possible osteomyelitis. Intravenous antibiotics were started and NPWT was continued through week 14, at which time a weekly PCMP application was initiated. The wound measured 10 cm² and was noted to have granulation tissue with moderate serosanguinous drainage and no bone exposed. A group 2 support surface was used for offloading with repositioning every 2 hours. After 4 PCMP applications, the wound measured 1.75 cm² and was healed 2 weeks later with complete epithelialization (Figure 2). 

Case 4: calciphylaxis ulcer

A 62-year-old woman with diabetes mellitus and end-stage renal disease on hemodialysis and multiple comorbidities presented with an unstageable ulcer on the right medial lower leg measuring 5.4 cm² with 100% necrotic eschar, subsequently confirmed as calciphylaxis. At week 9, after local wound care with silver hydrogel and gauze failed to achieve improvement, PCMP was applied to the full-thickness wound, which then measured 5 cm² with 80% granulation tissue and 20% slough. The patient was hospitalized, and the PCMP was not changed and left in situ for 2 weeks. At week 12, sharp debridement was performed and PCMP was reapplied weekly for 2 applications. The patient course was then complicated with another hospitalization unrelated to her ulcer, and, at week 16, PCMP was reapplied for 1 application. At week 20, the ulcer was noted to be healed with complete epithelialization (Figure 3). 

Case 5: venous leg ulcer

A 77-year-old woman with diabetes mellitus and a complicated cardiovascular history including venous insufficiency presented with a left lateral leg ulcer that had been previously treated with NPWT. The ulcer measured 203.5 cm² with cellulitis and serosanguinous drainage, 60% granulation tissue, and 40% slough. The ulcer was previously complicated with a hematoma and bleeding, and the patient was not felt to be a candidate for a split-thickness skin graft due to her frail skin and venous insufficiency. Nonselective debridement was performed and local wound care and compression therapy were initiated. At week 5, PCMP was applied to the ulcer measuring 166.5 cm² and applied weekly for a total of 4 applications, along with compression therapy. The last PCMP treatment was applied at week 8, when the wound measured 96.25 cm², and the ulcer healed with complete epithelialization by week 16. 

Case 6: traumatic wound

During the same episode of care described in case 5, the patient sustained a large traumatic hematoma on the right anterior lower leg measuring 80 cm² with erythema and edema. Initial treatment included debridement, moist wound dressings, and compression. At week 3, PCMP was applied to the wound measuring 39 cm² with 80% granulation tissue and 20% slough. Weekly PCMP applications continued for 10 weeks along with good standard care, including compression. At week 16, the wound measured 3.6 cm² (Figure 4), but the patient was subsequently lost to follow-up. 

Case 7: sacral pressure ulcer

A 79-year-old woman with diabetes mellitus and a history of chronic kidney disease, Alzheimer’s disease, and peripheral vascular disease presented with an infected Stage 3 sacral pressure ulcer measuring 25 cm² with no exposed bone, but with necrotic tissue. After osteomyelitis was confirmed, intravenous antibiotics were started, and offloading was initiated with group 2 support surface and local wound care, including application of a silver dressing. At week 8, PCMP was applied to the ulcer measuring 12 cm² with minimal serosanguinous drainage. The patient then was admitted to the hospital for aspiration pneumonia and was lost to follow-up during that time. At week 11, PCMP was reapplied for 3 more applications, but the patient was subsequently readmitted for altered mental status. At week 17, PCMP was reapplied for 4 more applications, with the last application at week 22; the wound then measured 2.7 cm². At week 24, the ulcer measured 2.0 cm², and the patient was lost to follow-up. 

Case 8: dehisced incision

A 79-year-old man with a history of chronic obstructive pulmonary disease, dementia, and spinal stenosis underwent lumbar nerve decompression surgery and developed a dehisced incision site with infection. At his initial visit, the patient presented with a midline lumbar full-thickness surgical wound measuring 0.78 cm² with 90% granulation tissue, 10% necrotic tissue, and erythema with no exposed bone. Cultures were positive for extended-spectrum β-lactamase–producing Escherichia coli, and intravenous antibiotics and NPWT were started. At week 6, PCMP was applied to the wound measuring 0.35 cm² with 90% granulation tissue and 10% slough. The PCMP was applied weekly for a total of 3 applications, with the last application at week 8 measuring 0.21 cm², followed by a silver dressing at week 9. By week 12, the wound had healed and complete epithelialization was noted. 

Case 9: diabetic foot ulcer

A 52-year-old woman with diabetes, chronic kidney disease, multiple cardiovascular comorbidities, and prior fifth toe amputation presented with a Wagner Grade 3 ulceration of the right lateral foot measuring 22.75 cm² with no bone exposed. The ulcer was surgically debrided and was treated with NPWT and offloading. At week 8, PCMP was applied in conjunction with NPWT to the ulcer measuring 7.2 cm² and applied weekly for 3 applications, with improvement and new epithelialization on the edges. The last PCMP application was on week 10, after which NPWT was discontinued and treatment with an iodine-based gel was initiated. By week 17, the ulcer had healed with complete epithelialization. 

Essentially, all chronic wounds are believed to be contaminated or colonized with bacteria, and excessive bioburden has long been recognized as a barrier to wound healing.^4,9 However, it is increasingly understood that the development of biofilm communities, rather than planktonic bacteria, plays a key role in stalling wound healing.^4,9,20,27 Biofilms develop when planktonic bacteria attach to the wound surface and produce a protective film of extracellular polymeric substances (EPS) that helps enhance and secure their attachment.¹⁵ As the microbes divide, they develop self-sustaining microcolonies that eventually detach and disseminate to colonize other surfaces.^15,17 Within the wound, biofilms stimulate a chronic inflammatory response that promotes the accumulation of neutrophils and macrophages that secrete high levels of free radicals and proteases.^8,11 Inflammatory protease concentrations in chronic wounds have been demonstrated to be 100-fold higher than inflammatory protease concentrations in normally healing acute wounds.⁵ This entraps the wound in a self-perpetuating inflammatory cycle, damaging tissues and impeding the healing process. 

Biofilm was first observed in chronic wounds in humans in 2008, when James et al¹³ reported that 60% of 50 chronic wound samples contained biofilm compared with only 6% (1/16) of acute wounds. Many experts now believe that nearly all chronic wounds have biofilm communities on at least part of the wound bed.^4,17,28 Despite this assumption, however, biofilms are often unrecognized, as they are microscopic structures that are not visible to the naked eye and do not usually cause typical clinical signs of infection.^4,14,17 Further, standard wound cultures performed by standard clinical microbiological laboratories detect single-cell planktonic bacteria rather than biofilm bacteria.⁴ Given these diagnostic challenges, it is reasonable to assume that all chronic wounds contain biofilm, and clinicians should manage them accordingly.^4,20,26

The management of biofilm presents unique challenges from that of their planktonic counterparts. The EPS matrix surrounding the biofilm bacteria protect these bacteria from antibiotic exposure, whereas the large numbers of inactive microbes with low metabolic activity are less susceptible to antibiotics, which target only metabolically active organisms.¹⁹ Although debridement effectively removes biofilm,^20,28 studies in experimental wound models and in patients with nonhealing venous leg ulcers^15,19 have shown that biofilms begin to reform within 24 hours after debridement and can fully mature within 3 days. Thus, although typical weekly debridement visits may remove mature biofilms, this schedule is insufficient to prevent biofilm from re-establishing at the wound site. Further, because biofilm resistance to antibiotics increases as the biofilm matures and the metabolic rate of the biofilm declines, the period immediately following debridement offers a window of opportunity for antimicrobial intervention. Indeed, studies^28-30 have shown biofilm phenotypes are more susceptible to antibiotics and biocides in the first 24 to 72 hours after debridement. 

With these considerations in mind, biofilm-based wound management (BBWM) has been proposed as a proactive strategy that utilizes topical antimicrobial therapy as a bridge between weekly debridement visits in an effort to both remove biofilm that has already formed and prevent it from reforming.^19,20 The use of BBWM was described by Wolcott and Rhoads²⁰ in a retrospective study involving 190 patients with diabetes mellitus and critical limb ischemia. Over a 4-year period, patients managed with a BBWM- centered algorithm achieved a 77% overall healing rate, which the authors considered to exceed reported healing rates in comparable patient populations managed with conventional strategies.²⁰ 

An important consideration for optimizing any BBWM strategy is to utilize an antimicrobial agent that effectively eradicates bacteria without disrupting healing processes. Whereas some antimicrobials are limited by a narrow spectrum of activity, others are limited by their nonselective range of activity, which renders them cytotoxic to bacterial and host cells.^25,31 For example, certain silver dressings eradicate bacteria as well as host keratinocytes and fibroblasts, leading to delayed healing.^31,32 Further, bacterial resistance to silver, albeit rare, has been reported.^33-35 Recognizing the need to balance antimicrobial efficacy with tissue compatibility, Müller and Kramer²⁵ developed a biocompatibility index for assessing antiseptics that weighs in vitro cytotoxicity agent microbicidal effects.In vitro assays demonstrated that PHMB and octenidine dihydrochloride had the most suitable biocompatibility index of the 11 antimicrobials tested, including povidone-iodine solution and ointment, chlorhexidine digluconate, and various silver preparations.²⁵

The use of PCMP represents an innovative approach for controlling biofilm formation while sequestering proteolytic enzymes and providing a biocompatible scaffold to support healing. In the present series of recalcitrant wounds, a combination of good conventional wound care and debridement followed by weekly PCMP applications proved to be an effective strategy for managing bioburden and supporting improvements in wound bed conditions and progression toward wound closure. Indeed, 6 of 9 wounds in this case series eventually healed, with an average time to closure of 10 weeks from the first PCMP application. These results are consistent with a previously reported experience²⁶ in which complete closure was achieved in 4 of 5 wounds after an average of 6.8 weeks following the first PCMP application. Wounds that fail to improve after bioburden has been effectively controlled may require therapy with bioengineered living cell-based products to restore growth factors, and cytokine signaling may be required to stimulate healing.²⁶

This case series demonstrates that the use of a purified collagen matrix combined with PHMB along with good wound care improved wound bed conditions and supported wound closure of recalcitrant, nonhealing wounds of various etiologies that had been refractory to wound healing with previous treatments. This strategy effectively delivers a broad-spectrum antimicrobial with high tissue compatibility in a native collagen matrix that can quench proteases and support healing. The success of this BBWM strategy demonstrates the importance of managing biofilm and high proteolytic activity to improve wound outcomes. 

Affiliation: Wayne UNC Health Care’s Wound Healing and Hyperbaric Center, Goldsboro, NC

Correspondence: Dimitrios Lintzeris, DO, CWS, Wayne Memorial Wound Healing and Hyperbaric Center, 2700 Wayne Memorial Drive, Goldsboro, NC 27534; 360woundcare@gmail.com

Disclosure: This analysis was funded in part by Organogenesis, Inc. (Canton, MA). Dr. Lintzeris serves as a consultant for Organogenesis and is a member of their speaker’s bureau. Writing assistance and editorial support during manuscript preparation and revision were provided by Julie Messick, PharmD, and Nathan B. Parsons, RN, BSN (Organogenesis).