Brill FHH1, Braunwarth H2 1 Dr. Brill + Partner GmbH Institut für Hygiene und Mikrobiologie, Hamburg, Germany 2 Coloplast GmbH, Hamburg, Germany

1. Comparison of Passive Bacteria Elimination versus Active
Bactericidal Efficacy in a quantitative in-vitro Agar Diffusion Assay
Brill FHH1, Braunwarth H2
1 Dr. Brill + Partner GmbH Institut für Hygiene und Mikrobiologie,
Hamburg, Germany
2 Coloplast GmbH, Hamburg, Germany
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2. Material & Methods I
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Method Quantitative kill method (Braunwarth et al. 2012)
Endpoints log10 reduction factor (RF) in relation to control dressing
Parallel tests 10
Contact time 24 h
Test bacteria Staphylococcus aureus, Pseudomonas aeruginosa
Test products Polyurethane Foam Dressing1 (passive elimination)
Hydrophobic Dressing2 (hydrophobic elimination)
Silicone Dressing3 (hydrophobic elimination)
Hydrocapillary Dressing4 (passive elimination)
Silver Polyurethane Foam Dressing5 (active kill).
Gaze with Water (control dressing)
1 Biatain Foam Dressing, 2 Cutimed Sorbact, 3 Cutimed Siltec, 4 Alione Hydrocapillary Dressing, 5 Biatain Ag Foam Dressing

3. 1. Spreading of test organism on TSA
2. Application of Wound dressings
3. Incubation for 24 h at 36 ºC
4. Extraction of agar below dressing
5. Agar homogenized (Stomacher) in
inactivation agent** to stop any
antimicrobial efficacy, measurement
of remaining bacterial count (BC)
6. Calculation of reduction factor (RF) =
log10 BC AMD – log10 BC WC water
Water Control (WC)
Zone of inhibition
Bacterial lawn
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Methods II*
Dressing
* Braunwarth H, Brill FHH, Brill H. Bacteriostatic and bactericidal in-vitro efficacy of antimicrobial wound dressings under organic load
conditions. Wundmanagament 06/2012: 266-269.
**80 g/L polysorbate 80, 60 g/L saponin, 8 g/L lecithin und 20 g/L SDS

4. Results (Reduction Factors)
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0
1
10
100
1000
10000
100000
1000000
10000000
100000000
1000000000
Silver Foam
Dressing
Foam Dressing Hydrocapillary
Dressing
Hydrophobic
Dressing
Silicone Dressing
Pseudomonas aeruginosa Staphylococcus aureus

5. Conclusion
► Passive elimination from wounds e.g. with polyurethane foam dressings may
lead to a significant reduction of bacterial load (90 – 99 %)
► This maybe through hydrophobic effects (see poster EP481 Braunwarth et
Brill, EWMA 2013)
► Antibacterial efficacy of a silver foam dressing is superior compared to passive
elimination (RF > 7)
► Depending on the clinical needs, the method of choice has to be selected
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