Impact of Cadexomer Iodine on Microbial Population of Chronic non-healing DFUs Complicated by Biofilm

19 Sep, 19

Introduction

Cadexomer iodine has demonstrated superior efficacy against microbial biofilms when tested in vitro and in animal models compared to other topical antimicrobials used in wound care dressings.

To determine the performance of cadexomer iodine against microbial populations from chronic non-healing diabetic foot ulcers (DFUs) complicated by biofilm in vivo, using molecular, microscopy and zymography methods.

Patient Profile

N= 17
Patients with a chronic non-healing DFU defined as a wound of >6weeks duration failing to respond to standard care

Table 1: Baseline patients demographics and wound metrics

Patient demographics
male	11(65%)
female	6(35%)
type 1 diabetes	2(12%)
type 2 diabetes	15 (88%)
mean age in years	66 (+13.6)
Wound metrics
location of ulcer
plantar metatarsal head	8
calcaneum	3
dorsal foot	2
ankle	2
hallux	2
duration of ulcer in weeks
mean duration of ulcer at baseline	25 (+20.7, range 6–72)
The University of Texas wound classification
1A	10(59%)
1C	1 (5.8%)
2A	5 (29.4%)
2C	1 (5.8%)
size of ulcer
mean DFU size at baseline	3.7x2.7 cm (L x W)

Methods

Cadexomer iodine was applied every second day over a 7-day treatment period (total of three applications).
A tissue biopsy was obtained from the wound edge for each participant before and after treatment.
All tissue samples were frozen – 80 degree Celsius until completion of the last patient and processed in bulk to reduce DNA sequencing and real-time quantitative PCR was used to determine the microbial load and diversity of tissue punch biopsies obtained pre- and post-treatment.

Scanning electron microscopy and/or fluorescence in situ hybridization confirmed the presence or absence of biofilm.
Zymography was used to determine levels of wound proteases.

Study Endpoints

Primary endpoint: Reduction in microbial load 7 days posttreatment.
Secondary endpoints: Exploration of community richness and diversity of DFUs pre- and post-treatment, visual changes to biofilm structures and alteration to levels of wound proteases matrix metalloproteinase (MMP-2 and MMP-9)

Results

Scanning electron microscopy and or fluorescence in situ hybridization confirmed the presence of biofilm in all samples
The median value of DFU biofilm architecture reduced between pre- and post-treatment samples
- pretreatment median was 4 (large microcolonies ~100 cells and a continuous film/matrix)
- post-treatment median was 3 (large microcolonies~100 cells)
The application of cadexomer iodine resulted in greater than a 1 log₁₀ reduction (mean microbial load pre-treatment=5.92 log₁₀16S copies/mg of tissue versus 4.56 log₁₀ 16S copies/mg of tissue, P=0.02) in 11 samples
The mean total MMP-9 and MMP-2 levels in eight samples reduced following 7 days application of cadexomer iodine
Reductions in the microbial load correlated to reductions in wound proteases pre- and post-treatment (P=0.03)
Cadexomer iodine demonstrated a broad level of antimicrobial activity in reducing both facultative anaerobes such as Staphylococcus spp., Serratia spp., Pseudomonas spp. and obligate anaerobes including Clostridiales family XI

Table 2: Pre- and post-treatment community diversity in microorganisms contributing to.5% abundance of each individual sample

	Samples	Average abundance (%)	Aerotolerance
Genera	Samples	Average abundance (%)	Aerotolerance
Pre-treatment
*Pseudomonas spp.*	5	58.5	Aerobe
*E01-9C-26 Marine*	4	11.2	Unknown
*Staphylococcus spp.*	4	58	Facultative
*Rhodothermaceae spp.*	3	5	Unknown
*Finegoldia spp.*	3	7.8	Anaerobe
*Elizabethkingia meningoseptica*	3	6.3	Aerobe
*Cornyebacterium spp.*	3	5.3	Aerobe
*Peptoniphilus spp.*	2	9.5	Anaerobe
*Ananerococcus spp.*	2	9.2	Anaerobe
*Proteus penneri*	2	20.5	Facultative
Post-treatment
*E01-9C-26 Marine*	8	10	Unknown
*ARKDMS49*	7	5.7	Unknown
*Cenarchaeum*	5	5.1	Unknown
*Cyanobacteria—subsection I*	5	7.4	Unknown
*Rhodothermaceae spp.*	4	5.8	Unknown
*Rhodothalassium spp.*	3	7	Unknown
*Cornyebacterium spp.*	3	11	Aerobe
*Elizabethkingia meningoseptica*	3	6.6	Aerobe
*Staphylococcus spp.*	3	42.8	Facultative
*Proteus penneri*	2	39	Facultative

Conclusion

The molecular and microscopy techniques used in the study showed that cadexomer iodine was effective in reducing the microbial load of chronic nonhealing DFUs complicated by biofilm
DNA sequencing allowed the exploration of chronic non-healing DFU microbiome and provided useful insights that these wounds support complex polymicrobial communities
Molecular methods also demonstrated that cadexomer iodine had a broad level of antimicrobial activity in reducing both facultative anaerobes such as Staphylococcus spp., Serratia spp., Pseudomonas spp. and obligate anaerobes including Clostridiales family XI