SSF
Evaluation of Antimicrobial Wound Dressings with Different Modes of Action using a 3D Soft Tissue Biofilm Model Kristina Blom1*, Karl Persson1, Astrid Persson1, and Maria Werthén1 *Corresponding author • [email protected]. 1Medibiome AB, Mölndal, Sweden • www.medibiome.com.
Aim
Discussion
Results
The aim of the study was to analyse if biofilm formation can be prevented
• The mode of action of the SFF-Ag dressing is to release silver ions.
Qualitative (visual) assessment
in a clinically relevant in vitro 3D biofilm model1 by two wound dressings, a silver-containing
soft
silicone
foam
dressing
(SSF-Ag)
and
dialkylcarbamoyl chloride (DACC) impregnated gauze, with different
SSF-Ag showed complete ZOI. The synthetic soft tissue appeared clear and translucent equal to the sterility control.
DACC showed no clear ZOI. The tissue looked opaque and green, equivalent to SSF and the bacterial control.
The acellular synthetic soft tissue treated with this dressing appeared translucent and clear, and no biofilm growth was detected. Quantitative assessment showed that bacterial growth was prevented in tissue, and
antimicrobial modes of action; released silver ions or hydrophobic binding
only a limited number of bacterial counts were found inside the
of bacteria to DACC molecules.
dressing. No green colour change was observed, indicating the lack of expression of the virulence factor pyocyanin. • The tissue turned opaque and green when the DACC dressing was
Method
used. Also quantitative assessment showed bacterial growth in the 1. 3D acellular synthetic soft tissue containing collagen and serum proteins was cast in 12-well plates.
tissue to the same extent as the SSF dressing and bacterial control. The visual assessment was the same for both PAO1 challenge sizes, 4x103 and 2x104 (shown) CFU/ml.
Therefore, bacterial binding to DACC does not seem to prevent
2. Pseudomonas aeruginosa ATCC 15692 (PAOI) was inoculated at two different challenge concentrations: 4x103 and 2x104 CFU/ml. 3. Dressings were applied: SSF-Ag, DACC, and SSF (control).
1. Acellular synthetic soft tissue 2. Pseudomonas aeruginosa 3. Dressing
Confocal microscopy image showing P. aeruginosa biofilm as aggregates in the 3D soft tissue.2
bacteria from multiplying nor to prevent the expression of pyocyanin. Furthermore, bacterial load inside the DACC dressing was comparable
Quantitative assessment Viable counts in soft tissue • SSF-Ag prevented the bacterial growth with >log 7 CFU/ml compared to DACC, SSF and the bacterial control. • The bacterial load recovered from DACC was >log 10 CFU/ml, equal to SSF and the bacterial control.
Viable counts in dressing • SSF-Ag prevented the bacterial growth with >log 7 CFU/mm2 and was below level of detection (LoD = 1 log cfu/mm2) compared to DACC and SSF. • The bacterial load recovered from DACC was equal to SSF dressing at about log 10 CFU/mm2.
12
8 6 4 2
8
• that the release of an active substance is required to prevent P. aeruginosa biofilm formation and production of pyocyanin.
6
References
4 2
0 SSF
SSF-Ag
SSF-Ag = Mepilex Ag (Mölnlycke Health Care AB, Gothenburg, Sweden) SSF = Mepilex (Mölnlycke Health Care AB, Gothenburg, Sweden)
This study, using a clinical relevant in vitro 3D biofilm model, suggests:
• that the mode of action of DACC, to bind bacteria to a hydrophobic surface, does not prevent P. aeruginosa from multiplying, forming biofilm, and expressing the virulence factor pyocyanin.
10
Log CFU/mm2
5. Zone of inhibition (ZOI) and bacterial burden in acellular synthetic soft tissue and dressing were analyzed resulting in both qualitative and quantitative assessments.
Conclusion
12
10
Log CFU/ml
4. The inoculated soft tissues were exposed to the dressings for 24 h at 35±2°C.
to that of the control dressing.
4*10 3 Start 4*10^3
DACC Bacteria control 4*10 4 Start 2*10^4
Aim
Discussion
Results
The aim of the study was to analyse if biofilm formation can be prevented
• The mode of action of the SFF-Ag dressing is to release silver ions.
Qualitative (visual) assessment
in a clinically relevant in vitro 3D biofilm model1 by two wound dressings, a silver-containing
soft
silicone
foam
dressing
(SSF-Ag)
and
dialkylcarbamoyl chloride (DACC) impregnated gauze, with different
SSF-Ag showed complete ZOI. The synthetic soft tissue appeared clear and translucent equal to the sterility control.
DACC showed no clear ZOI. The tissue looked opaque and green, equivalent to SSF and the bacterial control.
The acellular synthetic soft tissue treated with this dressing appeared translucent and clear, and no biofilm growth was detected. Quantitative assessment showed that bacterial growth was prevented in tissue, and
antimicrobial modes of action; released silver ions or hydrophobic binding
only a limited number of bacterial counts were found inside the
of bacteria to DACC molecules.
dressing. No green colour change was observed, indicating the lack of expression of the virulence factor pyocyanin. • The tissue turned opaque and green when the DACC dressing was
Method
used. Also quantitative assessment showed bacterial growth in the 1. 3D acellular synthetic soft tissue containing collagen and serum proteins was cast in 12-well plates.
tissue to the same extent as the SSF dressing and bacterial control. The visual assessment was the same for both PAO1 challenge sizes, 4x103 and 2x104 (shown) CFU/ml.
Therefore, bacterial binding to DACC does not seem to prevent
2. Pseudomonas aeruginosa ATCC 15692 (PAOI) was inoculated at two different challenge concentrations: 4x103 and 2x104 CFU/ml. 3. Dressings were applied: SSF-Ag, DACC, and SSF (control).
1. Acellular synthetic soft tissue 2. Pseudomonas aeruginosa 3. Dressing
Confocal microscopy image showing P. aeruginosa biofilm as aggregates in the 3D soft tissue.2
bacteria from multiplying nor to prevent the expression of pyocyanin. Furthermore, bacterial load inside the DACC dressing was comparable
Quantitative assessment Viable counts in soft tissue • SSF-Ag prevented the bacterial growth with >log 7 CFU/ml compared to DACC, SSF and the bacterial control. • The bacterial load recovered from DACC was >log 10 CFU/ml, equal to SSF and the bacterial control.
Viable counts in dressing • SSF-Ag prevented the bacterial growth with >log 7 CFU/mm2 and was below level of detection (LoD = 1 log cfu/mm2) compared to DACC and SSF. • The bacterial load recovered from DACC was equal to SSF dressing at about log 10 CFU/mm2.
12
8 6 4 2
8
• that the release of an active substance is required to prevent P. aeruginosa biofilm formation and production of pyocyanin.
6
References
4 2
0 SSF
SSF-Ag
SSF-Ag = Mepilex Ag (Mölnlycke Health Care AB, Gothenburg, Sweden) SSF = Mepilex (Mölnlycke Health Care AB, Gothenburg, Sweden)
This study, using a clinical relevant in vitro 3D biofilm model, suggests:
• that the mode of action of DACC, to bind bacteria to a hydrophobic surface, does not prevent P. aeruginosa from multiplying, forming biofilm, and expressing the virulence factor pyocyanin.
10
Log CFU/mm2
5. Zone of inhibition (ZOI) and bacterial burden in acellular synthetic soft tissue and dressing were analyzed resulting in both qualitative and quantitative assessments.
Conclusion
12
10
Log CFU/ml
4. The inoculated soft tissues were exposed to the dressings for 24 h at 35±2°C.
to that of the control dressing.
4*10 3 Start 4*10^3
DACC Bacteria control 4*10 4 Start 2*10^4
