The Effect of Negative Pressure Wound Therapy with and without Instillation on Mature Biofilms In Vitro

Shamaila Tahir; Matthew Malone; Honghua Hu; Anand Deva; Karen Vickery

doi:10.3390/ma11050811

The Effect of Negative Pressure Wound Therapy with and without Instillation on Mature Biofilms In Vitro

Materials (Basel). 2018 May 16;11(5):811. doi: 10.3390/ma11050811.

Authors

Shamaila Tahir¹, Matthew Malone^{2

3

4}, Honghua Hu⁵, Anand Deva⁶, Karen Vickery⁷

Affiliations

¹ Surgical Infection Research Group, Faculty of Medicine and Health Sciences, Macquarie University, Sydney 2109, Australia. shamaila.tahir@students.mq.edu.au.
² Infectious Diseases and Microbiology, School of Medicine, Western Sydney University, Sydney 2751, Australia. matthew.malone@westernsydney.edu.au.
³ Liverpool Diabetes Collaborative Research Unit, Ingham Institute of Applied Medical Research, Sydney 2170, Australia. matthew.malone@westernsydney.edu.au.
⁴ High Risk Foot Service, Liverpool Hospital, South West Sydney LHD, Sydney 2170, Australia. matthew.malone@westernsydney.edu.au.
⁵ Surgical Infection Research Group, Faculty of Medicine and Health Sciences, Macquarie University, Sydney 2109, Australia. helen.hu@mq.edu.au.
⁶ Surgical Infection Research Group, Faculty of Medicine and Health Sciences, Macquarie University, Sydney 2109, Australia. anand.deva@mq.edu.au.
⁷ Surgical Infection Research Group, Faculty of Medicine and Health Sciences, Macquarie University, Sydney 2109, Australia. karen.vickery@mq.edu.au.

Abstract

Background: To investigate the effect of negative pressure wound therapy (NPWT) with and without instillation (NPWTi) on in vitro mature biofilm.

Methods: Mature biofilms of Pseudomonas aeruginosa and Staphylococcus aureus were grown under shear (130 rpm) on polycarbonate coupons in a CDC biofilm reactor for 3 days. Coupons containing biofilms were placed in a sterile petri dish and sealed using NPWT or NPWTi. Coupons were exposed to treatment for 24 h with NPWT alone or with instillation of: Povidone iodine solution (PVP-I) (10% w/v equivalent to 1% w/v available iodine, BETADINE^®, Mundipharma, Singapore), surfactant based antimicrobial solution with polyhexamethylene biguanide (SBPHMB) (Prontosan^®, B Braun Medical, Melsungen, Germany), Gentamicin 1 µg/mL (GM) (G1264 Sigma-Aldrich Pty Ltd., Castle Hill, Australia) Rifampicin 24 µg/mL (RF) (R3501 Sigma-Aldrich Pty Ltd., Castle Hill, Australia) and NaCl 0.9% (Baxter, Deerfield, IL, USA). Bacterial cell viability and biofilm architecture pre-and post-treatment were assessed using colony forming units (cfu), Live/Dead viability staining, confocal laser scanning microscopy (CLSM) and scanning electron microscopy (SEM).

Results: Significant reductions were obtained in S. aureus biofilm thickness (65%) and mass (47%) when treated with NPWTi as compared to NPWT only. NPWTi with instillation of SBPHMB, PVP-I and RF achieved between 2 and 8 log₁₀ reductions against S. aureus biofilm (p < 0.05⁻0.001). Conversely, PVP-I and SBMO achieved a 3.5 log₁₀ reduction against P. aeruginosa (p < 0.05).

Conclusions: NPWT alters biofilm architecture by reducing biofilm thickness and mass, but this does not affect bacterial cell viability. NPWT with instillation of certain antimicrobials solutions may provide a further synergistic effect in reducing the number of viable biofilm microorganisms. Our in vitro model may be used for screening the effectiveness of antimicrobials used under instillation prior to animal or human studies.

Keywords: biofilm; chronic wounds; in vitro; instillation therapy.