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: Passive Immunotherapy

In a preclinical rat wound model,[57] the effects of MPPT on wound healing and the immune response were measured. An aseptic abscess was induced by injecting an alkaline solution into the skin under local anesthesia. After the abscess had formed, it was opened surgically, then the animals were divided into 3 groups: MPPT, topical antibiotic (gentamicin in a polydimethylsiloxane absorbent powder), and untreated control. The products were applied once daily until reaching a clean wound (ie, free from necrosis, pus, and fibrinogenous thickenings). The group receiving MPPT reached the clean-wound stage 60% faster than the other groups, and the wounds closed significantly faster (the same degree of effect as reported in the comparative clinical study[54]). The study[57] was performed in young, still growing animals and only rats in the MPPT group gained weight during the study, whereas the other groups demonstrated impeded growth. Retarded growth is a very important indicator of an organism being exposed to severe stressors, and the weight gain in the MPPT group indicates that MPPT reduced the impact of the stress associated with the wound on the organism.

The speed of invasion of microorganisms into the wound was measured, and it was identical for the MPPT and the control groups, whereas the topical antibiotic had a significantly slower rate of invasion.[57] This demonstrates that MPPT does not inhibit normal wound colonization, which is consistent with its lack of antimicrobial effects and that an antibiotic, as expected, will delay invasion.

Swabs of the wounds were taken at regular intervals during the first 48 hours and analyzed for the presence of immune cells. It was found (eFigure 4[57]) that the topical antibiotic and the control groups both almost exclusively showed a presence of neutrophils throughout the measurement period, whereas the MPPT group had a faster and significantly stronger invasion of immune cells with a lower proportion of neutrophils and higher proportions and earlier presence of monocytes (precursor of macrophages) and lymphocytes.[57] Similar to macrophages (monocytes), lymphocytes are essential to healing. Comparing these findings (eFigure 4[57]) to the study in GF mice (eFigure 1[18]), the distribution and temporal pattern of immune cells in the MPPT group is very similar to the pattern seen in the faster healing GF mice (ie, a reduced proportion of neutrophils and an earlier presence and higher proportion of immune cells associated with the second phase of the immune response). This indicates that the application of MPPT results in a wound environment more closely resembling a GF state, in which the impact of the presence of microorganisms on the wound and on the immune response is reduced.

eFigure 4.

Presence of neutrophils, lymphocytes, and monocytes in the wound at 4 time points following opening of the abscess.
N=15/group (mean ± standard deviation).
◆: MPPT; ■: topical antibiotic; ▲: control
Figure adapted from Bilyayeva et al.57 Reprinted with permission from Willingsford Ltd, Southampton, United Kingdom.

Clinical findings[54–56] and veterinary use of MPPT for wound care have consistently shown MPPT will remove critical colonization and local infections from wounds and support healing. Micropore particle technology lacks antimicrobial action and uses only physical actions for the removal of wound exudate, but it is a powder that is in direct, close contact with the wound surface. Here, the micropumping action will effectively remove any wound exudate, and this action will simultaneously remove the toxins and degrading enzymes secreted by bacteria and fungi into the wound exudate to inhibit the immune system. The removal of these toxins and enzymes will enable the immune system to recover and regain its ability to control the composition of the microbiome, such as selectively killing unwanted microorganisms. Also, as aforementioned, MPPT will create holes by suction in biofilm, which consists of 90% to 95% water, and this will furthermore enable the immune cells to enter the biofilm and reach microorganisms hiding within. Together, these effects of MPPT essentially would disrupt the 2 primary defense systems of bacteria and fungi; thus, it would act as a passive immunotherapy that returns the control of the microbiome and the healing process to the immune system. It can, thereby unhindered, remove unwanted microorganisms to reach the composition or balance of microorganisms in the microbiome the body seeks. These actions would be consistent with the immune responses seen in the preclinical study[57] as well as with the observation in PG that a persistent change is seen in the wound environment. Finally, this mode of action also has the advantage that it will not be limited by or contribute to antimicrobial resistance, because it is based solely on physical action.

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