Antimicrobial effects of a borate-based bioactive glass wound matrix on wound-relevant pathogens

Introduction: Colonization of pathogens in wounds significantly inhibits wound healing and is a major factor in the failure of wounds treated with skin grafts and skin substitutes.  Synthetic materials such as bioactive glass are known to have antimicrobial effects and are becoming commercially relevant as the next generation of skin substitutes [1-2].  The antimicrobial effects of a borate based bioactive glass matrix (BGWM) on nineteen wound relevant pathogens was studied using the in-vitro AATCC 100 test method [3]. Methods:A total of 19 microbial strains, including five Gram-positive, five Gram-negative, four yeast, and five mold strains of clinical significance were investigated. All microbial strains were stored as 20% glycerol stocks at -80°C. Bacteria and yeasts were streaked on tryptic soy agar (TSA) plates and stored at 4°C up to two weeks. However, mold stocks were stored for up to four weeks at 4°C. A total of 312 BGWM samples from two separate lots were studied for antimicrobial activity. Antimicrobial efficacy of the BGWM was determined according to a modified version of AATCC TM100-2019 [4]. The samples were placed in individual sterile 100 mm x 15 mm Petri dishes, followed by the addition of 6 mL of SWF, and then transferred to a stationary humidified incubator at 37°C (bacteria and yeast) or 25°C (mold) for 7 days to precondition. The remaining samples were incubated for an additional 1 day, 4 days or 7 days, then transferred individually to 50 mL centrifuge tubes containing 30 mL of D/E broth for sonication, recovery, and plating as described above. Each material was evaluated in triplicate, and the experiment was performed once per species. Results:The reduction of viable gram negative and gram positive bacteria and yeasts at 4 and 7 days post culture onto the BGWM was significant ( > log 4) in most cases.  Mold counts were reduced (