This study assessed the absorbency and retention of microorganisms by four different wound dressings. The dressings were exposed to fluid containing bacteria and yeast, and the absorbency and levels of residual microorganisms were measured over 24 hours. Dressing 2 absorbed the most fluid and retained the highest levels of microorganisms compared to the other dressings tested. The results suggest Dressing 2 is most effective at managing wound exudate and sequestering harmful bacteria.

1. In vitro Assessment of Absorbency
and Retention of Microorganisms
Authors: Professor Val Edwards-Jones1
(Presenter), Pam Spruce2
1. Manchester Metropolitan University, Manchester, UK v.e.jones@mmu.ac.uk
2. TVRE Consulting, Stoke-on-Trent, UK. pamspruce@gmail.com

2. Authors: Professor Val Edwards-Jones1
(Presenter), Pam Spruce2
In vitro Assessment of Absorbency and Retention of Microorganisms
Chronic wound exudate contains harmful bacteria, which can delay healing. Absorbent dressings
have an important role in managing wound exudate and sequestration of bacteria.
AIM:
To determine the absorbency, sequestration and retention of microorganisms by four dressings used
in wound management.
METHODS:
Phosphate buffered saline (PBS) containing a known number of microorganisms was allowed to
absorb into four different wound dressings under 60mm Hg pressure. The numbers of residual
organisms in the PBS and the amount absorbed into the dressings was determined at 4 and 24hrs.
Four microorganisms were used, Escherichia coli, Pseudomonas aeruginosa, Methicillin-resistant
Staphylococcus aureus and Candida albicans.
Following completion of the sequestration studies the dressings were removed from the model
and placed in the 37o
C incubator until fully dried. The dressings were then accurately weighed to
determine the biomass.
Authors: Professor Val Edwards-Jones1
(Presenter), Pam Spruce2

3. Authors: Professor Val Edwards-Jones1
(Presenter), Pam Spruce2
In vitro Assessment of Absorbency and Retention of Microorganisms
RESULTS:
1. Fluid absorption
A similar amount of fluid was absorbed by all four dressings at 4hrs. Dressing 2 absorbed the highest
volume over the 24hr period. (Table 1)
Authors: Professor Val Edwards-Jones1
(Presenter), Pam Spruce2
Table 1 Absorbed in model
(ml)(SD) after 4hrs
Absorbed in model
(ml)(SD) after 24hrs
Dressing 1 8.29 (0.1) 13.3 (0.59)
Dressing 2 8.34 (0.1) 14.03 (0.38)
Dressing 3 8.29 (0.1) 10.79 (0.65)
Dressing 4 8.14 (0.3) 12.25 (0.25)

4. Authors: Professor Val Edwards-Jones1
(Presenter), Pam Spruce2
In vitro Assessment of Absorbency and Retention of Microorganisms
RESULTS:
2. Retention and sequestration of microorganisms
The sequestration and retention of microorganisms into the dressings varied depending upon
microorganism and the time period. (Table 2 and 3)
Authors: Professor Val Edwards-Jones1
(Presenter), Pam Spruce2
Table 2 (4hrs)
MRSA P.aeruginosa E.coli C.albicans
Dressing 1 96% 26.9% 27% 99%
Dressing 2 82.1% 46% 4.5% 99%
Dressing 3 88.7% 11.5% 4.5% 98%
Dressing 4 81% 50% 13.6% 96%

5. Authors: Professor Val Edwards-Jones1
(Presenter), Pam Spruce2
In vitro Assessment of Absorbency and Retention of Microorganisms
All the dressings reduced the bacterial numbers in the residual fluid at both 4hrs and 24hrs, but
this varied depending upon the dressing and the microorganism. Dressing 2 reduced numbers of
organisms between 25-99% at 24hrs.
Authors: Professor Val Edwards-Jones1
(Presenter), Pam Spruce2
Table 3 (24hrs)
MRSA P.aeruginosa E.coli C.albicans
Dressing 1 41% 20% 29.4% 95%
Dressing 2 97.6% 38% 25% 99.7%
Dressing 3 80% 90% 45.3% 98.7%
Dressing 4 54.4% 36% 5.9% 84%

6. Authors: Professor Val Edwards-Jones1
(Presenter), Pam Spruce2
In vitro Assessment of Absorbency and Retention of Microorganisms
RESULTS:
3. Biomass
Biomass is a good indicator of organism retention in the dressing. In this model system the organism
would have been able to move freely between the dressing and the fluid.
If the organism is retained within the dressing then the weight of the dressing would
increase. This was observed in all cases, but Dressing 2 showed the greatest increase in weight
compared to the other dressings tested. (Table 4)
Authors: Professor Val Edwards-Jones1
(Presenter), Pam Spruce2
Biomass (mg) MRSA P.aeruginosa E.coli C.albicans
Dressing 1 80 75 80 50
Dressing 2 100 90 80 60
Dressing 3 40 35 55 10
Dressing 4 65 75 95 55
Table 4

7. Authors: Professor Val Edwards-Jones1
(Presenter), Pam Spruce2
In vitro Assessment of Absorbency and Retention of Microorganisms
CONCLUSIONS:
The dressings included in this study demonstrated similar properties. However within this
methodology, Dressing 2 was observed to be more absorbent and to retain more microorganisms
than the others.
It was interesting to observe that the retention of microorganisms in the dressing varied depending
upon their Gram type. This may have been due to an electrostatic interaction between the
microorganism and the dressing. This would be interesting to investigate, and warrants further study.
DRESSING REFERENCES:
Dressing 1: Advadraw (Advancis)
Dressing 2: Drawtex®
(Beier Drawtex Healthcare)
Dressing 3: Aquacel Extra (Convatec)
Dressing 4: Urgoclean (UrgoMedical)
This study was supported by an educational grant from Martindale Pharma
Authors: Professor Val Edwards-Jones1
(Presenter), Pam Spruce2