Time to Abandon Antimicrobial Approaches in Wound Healing

A Paradigm Shift

Jeanette Sams-Dodd, BSc, BScVet; Frank Sams-Dodd, PhD, Dr.med

Disclosures

Wounds. 2018;30(11):345-352. 

In This Article

MPPT

Micropore particle technology (MPPT) is a different approach to wound care that does not depend upon antimicrobial action. It (Acapsil [Willingsford Ltd, Southampton, UK]; SertaSil [Willingsford Ltd]; Amicapsil [Willingsford Ltd]; Aprobaxil [Willingsford Ltd]) consists of fine, highly porous particles that absorb wound exudate into a micropore structure (eFigure 2). Here, capillary action pulls the exudate away from the wound surface towards the upper surface of the MPPT layer, where a highly expanded surface area facilitates effective evaporation. The MPPT essentially acts as small micropumps, which, due to their small size, are able to access all crevices in the wound surface. MPPT has not shown any indications of causing cytotoxicity.

eFigure 2.

Micropore particle technology (MPPT) mode of action. The MPPT will not over-dry the wound surface, because the particles will retain a certain level of moisture. Capillary action automatically will stop if no excess fluid is present, ensuring a moist, but not wet, wound surface.
Reprinted with permission from Willingsford Ltd, Southampton, United Kingdom.

As shown in eTable 2, MPPT lacks in vitro antimicrobial action. One gram of MPPT was added to 100 mL tryptone soya broth (TSB) and 5 mL of the mixture was pipetted into each of 8 MPPT Petri dishes, 5 mL of pure TSB was pipetted into each of 8 control Petri dishes, and 0.1 mL of suspension of each bacterial strain to be evaluated (~1 x 103 CFU/mL) was added to 2 Petri dishes of each group. Molten tryptone agar was added to each Petri dish, mixed, and allowed to settle. The strains evaluated were Pseudomonas aeruginosa, S aureus, Bacillus subtilis, and Candida albicans. The plates were incubated for 4 days at 30°C, after which the number of colonies were counted. The number of organisms recovered in the MPPT group was similar to the control, demonstrating MPPT does not have any antimicrobial effects on bacteria or fungi.

In collaboration with Dr. M. Alhede from the Biofilm Test Facility, University Hospital of Copenhagen (Copenhagen, Denmark), the effects of MPPT on biofilm were evaluated.[52,53] Three separate cultures, each with 4 replicates, were established of P aeruginosa. The surface of the biofilm was exposed directly to the air. One culture was the control, a second had 3 mm of MPPT applied onto the surface of the culture at 0 hours, and a third culture had 3 mm of MPPT applied at 24 hours.[53] All cultures were analyzed at 48 hours, which corresponds to a mature biofilm culture. The samples were rinsed and 1 culture from each dish was photographed and the thickness of the cultures was determined by confocal laser scanning microscopy.[53]

As shown in eFigure 3, MPPT disrupted the surface of the cultures, but it did not inhibit the ability of the bacteria to produce biofilm, which can be seen by the increased thickness of the cultures. In a separate experiment, MPPT was applied at 32 hours and washed off at 48 hours, and, at 72 hours, the cultures were sectioned and dyed to image any dead cells; the procedure was selected to resemble the clinical use of MPPT. The MPPT group did not show any signs of increased numbers of dead bacteria.

eFigure 3.

Pseudomonas aeruginosa biofilm were obtained from a static culture and placed on a cellulose filter on top of agar in a Petri dish using an ABTG minimal culture medium consisting of salts and glucose.52 (A) Petri dishes with biofilm cultures at 48 hours. Note how the 0-hours culture has extended its growth pattern away from the area where the micropore particle technology (MPPT) was applied. (B) Effects of MPPT application at 0 hours and 24 hours on P aeruginosa biofilm. The biofilm cultures were analyzed when they were 48 hours old. The thickness of the biofilm is shown below the images. (C) Effects of MPPT on bacterial survival in the biofilm. Dead bacteria are dyed red. Bar represents 500μm.
ABTG: Agrobacterium medium containing thiamine and glucose
Figure courtesy of Dr. M. Alhede, Department of Clinical Microbiology, Rigshospitalet, Copenhagen, Denmark. Reprinted with permission from Willingsford Ltd, Southampton, United Kingdom.

Micropore particle technology has been evaluated in a randomized, comparative clinical study with 266 patients.[54] The effects of MPPT on the healing of critically colonized to locally infected wounds, diabetic foot and venous leg ulcers, and burns were compared with a topical antibiotic (gentamicin in a polydimethylsiloxane absorbent powder) and to an antiseptic (iodine/dimethyl sulfoxide [DMSO] combination, where DMSO improves iodine tissue penetration). Bilyayeva et al[54] found MPPT, relative to the antibiotic and the antiseptic, reduced the time to reaching a wound free of necrosis, pus, and infection by 60% and initiated 50% faster onset of granulation and epithelialization; the effects were independent of wound type. In addition, MPPT reduced hospitalization days by 41% for acute wounds, 31% for diabetic foot ulcers, and 19% for venous leg ulcers relative to the antibiotic and by 44%, 51%, and 36%, respectively, relative to the antiseptic. These effects appeared to correlate with the degree of underlying disease processes.

In addition, MPPT has been evaluated at Bristol University Hospital[55] on 9 dehisced surgical wounds and 1 category 4 pressure ulcer. Most of the wounds displayed > 40% slough and signs of local infection. The MPPT was applied once daily for 2 to 5 days, and this was sufficient to reach a clean, actively healing wound and facilitate a rapid build-up of granulation tissue. All wounds continued towards full closure much faster than normal. No adverse events were reported. Standard of care normally would have consisted of, on average and assuming no complications developed, 1 week with UrgoClean (URGO Medical, Paris, France) followed by 2 or more weeks with negative pressure wound therapy to reach a stage where exudate level and critical colonization were under control and the wound had initiated healing (ie, the stage reached in 2–5 days with MPPT).

At University Hospitals Birmingham, MPPT was evaluated in 3 cases of stable, inactive, chronic pyoderma gangrenosum (PG) ulcers.[56] The patients were on immunosuppressants (mycophenolate mofetil), antibiotics (doxycycline), and corticosteroids (dermovate). Micropore particle technology was applied to the ulcers once daily for 5 days. In all patients, increased granulation, reduced slough, and controlled exudate were seen, and the ulcers continued to improve 2 to 3 months after the last application (latest observation). In 1 patient, the dose of immunosuppressant was reduced.

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