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Bacteriostic Properties: Harrow, J

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A comparison of the effects of two hydrogels upon the
proliferation of three micro-organisms of importance for
chronic wound care

 

Introduction
Debridement of devitalised tissue is essential for successful wound healing, as formation of granulation tissue requires a clean wound bed. Devitalised tissue that may have an imbalance of bacteria may retard the healing process. Amorphous hydrogels are primarily designed to promote autolytic debridement of devitalized tissue.


Hydrogels contain polymers, or gelling agents that influence the hydrogels consistency. IntraSite* Gel, with its patented formulation, also contains a humectant propylene glycol which helps prevent the hydrogel from drying
out and forms a smooth pliable dressing to aid application. However, most importantly, propylene glycol helps to preserve the sterility of the dressing due to its bacteriostatic properties.


Aim
To compare the in-vitro proliferation of three different micro-organisms when grown in Intrasite Gel or Purilon TM gel over a time period of 72 hours.


Method
Each gel was inoculated with heat inactivated horse serum containing 102 cfu / ml of each of the test organisms at a ratio of 1g of gel : 1ml of serum. Serum controls were also set up containing 102 cfu / ml of each test organism.

 

All test and control samples were thoroughly mixed and incubated at 32°C. At sample times of 0, 4, 24 and 72 hours the number of viable organisms present in each sample was determined by the pour plate technique.


Objectives

  • To assess if there were any differences in the micro-organisms present between IntraSiteGel and Purilon gel over the time period.
  • To assess if there were any differences in the count of micro-organisms present between IntraSite Gel and the control and between Purilon** gel and the control over the time period.


Results
The effect of IntraSite Gel and Purilon gel on microbial proliferation was compared by inoculating each test gel with either S. aureus, P. aeruginosa or C. albicans. Serum controls were also set up to evaluate the growth of each test organism in serum alone.

 

Figure 1

 

  The cfu/ml of S.aureus for Intrasite Gel and Purilon Gel

Mean log10 count/ml +/-

S.D.

Intrasite Gel vs Purilon Gel Figure 1
  Time (hrs)
 
  Intrasite gel   Purilon   Control

Figure 2

  The cfu/ml of P.aeruginoa for Intrasite Gel and Purilon Gel
Mean log10 count/ml +/- S.D. Intrasite vs. Purilon Gel figure2
  Time (hrs)
 
  Intrasite gel   Purilon   Control

Figure 3

  The cfu/ml of C.albicans for Intrasite Gel and Purilon Gel
Mean log10 count/ml +/- S.D. Intrasite vs. Purilon figure 3
  Time (hrs)
 
  Intrasite gel   Purilon   Control

Intrasite Gel showed bacteriostatic activity against the bacteria S.aureus and P.aeruginosa(figure 1&2) and fungistatic activity against C.albicans (figure 3). P.aeruginosa proved to be the most sensitive organism to Intrasite gel, with numbers of this organism being reduced to below detectable levels by the 72 hour time point, (p<0.0001) at each time point), (figure 2). the test results showed that there was a statistically significant difference in the mean log count of>S.aureus, P.aeruginosa and C.albicans between IntraSite Gel and Purilon at times 4, 24, and 72 hours (p<0.0001 at each of these time points).>

 

During the study, the mean log counts of the micro-organisms were higher for Purilon** than for the control. There was an observed statistically significant
difference in the mean log count of both S.aureus and C.albicans between Purilon and the control at 24 and 72 hours, with the mean log count for both these micro-organisms being higher for Purilon than for the control. Similarly, the mean log count of P.aeruginosa was higher for Purilon** than for the control at 24 hours and showed statistical significance.


Conclusions
IntraSite Gel and Purilon gel are both hydrogel wound dressings designed to promote the debridement of necrotic tissue. However, the two dressings showed contrasting properties in their ability to control microbial proliferation. In the experiments carried out, IntraSite Gel showed bacteriostatic and
fungistatic activity in-vitro against three different test organisms. In contrast, Purilon gel showed no bacteriostatic properties against any of the test organisms.

 

 

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