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Summary

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  Iodosorb* 0.9% Cadexomer Iodine

 

 

 

 

A comparison of the antimicrobial activity of a cadexomer iodine dressing and a povidone iodine dressing

 

Introduction

This study compares the rapid and sustained antimicrobial activity of a Povidine Iodine dressing (Inadine - Johnson & JohnsonTM) with a Cadexomer Iodine dressing ( Iodosorb - Smith & Nephew). The antimicrobial activity of a single layer of Iodosorb was compared with four layers of Inadine. Multi layers of Inadine are often used in clinical practice to provide prolonged antimicrobial activity.

 

Replicates of both Iodosorb (single layer) and Inadine (four layers) were subjected to a repeated daily challenge with either Methicillin Resistant Staphylococcus aureus (MRSA) or Pseudomonas aeruginosa in the presence of serum, over a 3-day experimental period. It is well recognised that when present in wound exudate, serum can cause inactivation problems with iodine based products. This was therefore a further challenge to both of the dressings under evaluation.

 

 

Method

One 1.5 x 1.5cm 2 piece of Iodosorb and four 1.5 x 1.5cm 2 pieces of Inadine, arranged as four layers, were moistened with heat inactivated horse serum. Serum controls were also set up. Each test and control sample was challenged with 10 6 CFU/ml of each test organism using sample times of 0 and 30 minutes. 30 minutes was used to represent rapid bacterial kill. The number of viable organisms remaining at each sample time point was determined by the pour plate technique. Any residual iodine was inactivated by using an appropriate neutralizer (Tryptone Soya broth containing sodium thiosulphate, Tween 80 and lecithin), After 1, 2 and 3 days incubation at 32°C, the test dressings and controls were re-challenged with 10 6 CFU/ml of the relevant test organism.

 

Results

After 30 minutes of contact time, both Iodosorb and Inadine were initially found to be capable of reducing numbers of both MRSA and P. aeruginosa to below detectable levels (<10>1 CFU/ml) (Figures 1 & 2). Iodosorb was found to be capable of sustaining this level of activity on each subsequent re-challenge for the duration of the 3-day experimental period. In contrast, none of the Inadine replicates were able to achieve a reduction in numbers of either test organisms from Day 1 onwards.

 

By Day 3 Inadine did not reduce levels of MRSA or P.aeruginosa to below 10 6 after 30 minutes.

 

There was statistical evidence (p<0.0001) to suggest that the effect of days on the bacterial counts are related to the treatment type and that>Iodosorb significantly reduced (p<0.0001) the bacterial count of mrsa and>P.aeruginosa compared to Inadine from day 1-3.

 

Effect on MRSA

Summary - Graph 1

 

Fig.1: Comparison of the antibacterial activity and durability of a single layer of Iodosorb with four layers of Inadine using MRSA as the challenge organism Log10 CFU/ml

 

Effect on P.aeruginosa

Summary - Graph 2

 

Fig.2: Comparison of the antibacterial activity and durability of a single layer of Iodosorb with four layers of Inadine using P. aeruginosa as the challenge organism

Conclusions

A single layer of Iodosorb was found to be more effective than four layers of Inadine in achieving sustained antimicrobial activity over a 3 day repeat challenge test. These results show a statistical significance between the two dressing technologies evaluated (p<0.0001). whilst the manufacturers do indicate that inadine may need to be changed up to two times daily in the initial phase to maintain antimicrobial efficacy, these results show that comparatively, a cadexomer iodine based dressing, with its sustained activity, may require fewer dressing changes over a course of treatment which in turn has an impact from a cost effectiveness perspective (table 1).>

 

Table 1: Cost analysis comparing the costs of Inadine and Iodosorb

 

All costs are in £

Inadine versus Iodosorb
Total costs Inadine Iodosorb
Anti-microbial dressing^ £1.16 £3.90
Sterile gauze £0.22 £0.22
Fixing Tape £0.07 £0.07
Sterile dressing pack £0.75 £0.75

Cost of materials per change

£2.20 £4.94

Cost of nursing time per change

£17.00 £17.00

Total cost per dressing change

£19.20 £21.94

Number of changes over 3-day period*

3.00 1.00
Total cost over 3-day period £57.60 £21.94

 

^Number of dressings needed per change, and number of changes over a 3-day period based on in-vitro studyNursing costs from: Unit Costs of Health and Social Care 2002, by Ann Netten & Lesley Curtis. Personal Social Services Research Unit, University of Kent. Costs of materials from Drug Tariff, February 2003

 

As demonstrated in-vitro, the performance of these dressings are very different. The technologies on which these dressings are based are also very different. Iodosorb, a Cadexomer Iodine based product, has a unique mechanism that slowly releases iodine to provide sustained antimicrobial activity. This is compared with Inadine, a Povidone Iodine (PVP) dressing which has a release mechanism that did not provide any antimicrobial activity after Day 1 of this study. The above work therefore supports the literature that states that povidone iodine based products have short lived antimicrobial activity 1 and activity is decreased by exposure to organic substances. 2,3

Iodosorb* Dressing

 

References
1. Drosou A, Falabella A, Kirsner RS. Wounds, 2003; 15 (5): 149-166
2. Zamora JL. Al J Surg, 1986; 151: 400-406
3. LeVeen HH, LeVeen RF and LeVeen EG. Surgery, Gynaecology and Obstetrics, 1993; 176: 183-190
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