In-vitro Study Evaluating the Sustained Released Effects of Antimicrobial Products Against Methicillin-resistant Staphylococcus Aureus (MRSA)

Background: Wound matrices are designed to stimulate cell proliferation and new tissue growth.

Purpose: This study examines the sustained release of a wound matrix that contains a broad-spectrum antimicrobial, polyhexamethylene biguanide hydrochloride (PHMB).  PHMB has been previously shown to reduce wound bioburden.

Methods: An in vitro model was used to determine the antimicrobial activity of the following treatments: 1) Collagen Wound Matrix-AM (CWM-AM)*, 2) Collagen Wound Matrix-AM XT˟ (CWM-AM XT), 3) Collagen Wound Matrix aloneᵝ (CWMA), 4) Dermal Repair Scaffold-Ag°(DRSAg), 5) Collagen Extracellular matrix(CEM)^, 6) Matrix Wound Dressing (CWM)~, and 7) Matrix Wound Dressing-Agᵟ (MWDAg). Matrices were placed individual in well plates and submerged in a sterile PBS (phosphate-buffered saline) solution. Treatments were incubated for 0,1,4,7,10,14 and 21 days and applied over the inoculated tryptic soy agar plates with Methicillin Resistant staphylococcus aureus USA300 (MRSA) at two concentrations (104 and 108 CFU/ml). After 24 hours the zone of inhibition (ZOI) were measure using ImageJ 1.41o software.  

Results: Both CWM-AM and CWM-AM XT exhibited substantially higher ZOI areas than all of other treatment groups on every time point. Most importantly, these results showed very little fluctuations from day 7 up until day 21. Both CWM-AM and MWDA groups showed relatively minor areas against MRSA. While DRSAg and MWDAg showed constant values in their respective ZOI areas for every time point but at higher areas than CEM and MWD. DRSAg and MWDAg were significantly (p < 0.05) higher than both CEM and MWD at the higher MRSA concentration plates on day 4. Overall, our results confirm that both of the antimicrobials present on CWM-AM and CWM-AM XT showed a diffuse against MRSA after at least 21 days. Additional porcine studies are underway to substantiate these findings.  

Conclusion: These studies may have important clinical implications in the use of tissue matrices with antimicrobials to reduce costly wound infections.