Page 72 - OxyBand Research Background

Effect of High Oxygen Level on Antimicrobial Efficacy of Silver
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Introduction Results
!! Silver is widely used in topical gels and impregnated dressings as an antimicrobial !! The graphs show inhibition of MRSA and Pseudomonas isolates treated with Silver (0.5% AgNO 3 ) and 80%
for healing infected and chronic wounds. In vitro studies have demonstrated varied Oxygen compared to 0.5% AgNO 3 and 5% and 21% Oxygen and 50µl 1x PBS and varying concentrations of
performance of silver dressings. Many in vitro studies have compared dressings oxygen. Results are an average of about five replicates 10 ml drops of AgNO 3 or PBS treated culture.
however results between studies differ. In vitro methods for silver studies have
differed and outcomes measured vary, causing the comparison of results to be !! For MRSA treated with Silver Nitrate and 80% Oxygen there was a > 5-log drop when compared to the growth
difficult. Little clinical evidence is available to support results of in vitro studies. of the PBS-treated cells by the end of 24 hrs, with most of the cell reduction occurring in the latter 19 hrs
Clinically silver dressing performance has also varied. compared to the Silver Nitrate and 5% and 21% Oxygen that exhibited a 1 log difference.
!! Silver has demonstrated minimal antimicrobial effect against common !! For Pseudomonas treated with Silver Nitrate and 80% Oxygen there was an immediate (within 30 minutes)
wound organisms such as Pseudomonas and E Coli in hypoxic and a sustained kill of the Pseudomonas compared to the Pseudomonas treated with Silver Nitrate and 5%
environments until additional oxygen is added. Bioactivation and thus Oxygen, the Pseudomonas was not killed and with 21% Oxygen the Pseudomonas came back or quiescent
antimicrobial efficacy of silver may be dependent on oxygen to convert silver into and began to come back at 4 hours.
the antimicrobial cation Ag+.
!! Since infected and chronic wounds are typically hypoxic, the efficacy of current
treatments with silver might be improved by increasing the oxygen level in the
wound. OxyBand Wound Dressing has been shown to increase PO 2 in wounds.
The present study was conducted to determine whether additional oxygen (the %
oxygen in OxyBand) improves the antimicrobial efficacy of silver (silver nitrate
AgNO 3 ) on two clinical isolates, Pseudomonas aeruginosa and methicillin-
resistant Staphylococcus aureus (MRSA) both common in wounds.
Methods
!! Cultures of two isolates were grown on TSA+ blood (TSAB) plates. Plated
cultures were transferred into flasks of 100 ml TSA broth until cell density
approximately matching a 0.5 McFarland standard, ~ 108 CFU/ml of cells. Five ml
aliquots test tubes were treated with either AgNO 3 (0.5% final conc.) or sterile PBS
and placed into vented canisters with free flowing 5:90:5, 21:74:5, or 80:15:5
(O2:N2:CO2) gas (5%, 21%, 80% O2). Canisters were placed into 37°C orbital
shaking incubators set to 135 RPM. At 0.5, 2, 4, 6, and 24 hrs, 0.5 ml of the Conclusion
cultures were centrifuged, and resuspended in 0.85% sodium chloride, 1%
polysorbate 20, and 0.1% sodium thioglycolate solutions and cultures were drop- !! The results of the present study demonstrate 80% Oxygen combined with Silver (Silver Nitrate) is more
dilution plated (5 replicate 10 µl drops/ dilution) to determine the effect of the effective as an antimicrobial against MRSA and Pseudomonas in vitro, than Silver (Silver Nitrate) at either
AgNOB3B and OB2. Cultures were assayed for ATP using an Invitrogen ATP, hypoxic (5%) or ambient air (21%) levels of Oxygen. These results suggest there is an additive effect of higher
luciferin-luciferace kit to determine differences in cellular ATP concentrations, levels of Oxygen to Silver Nitrate in treating MRSA and Pseudomonas. The clinical significance of these
assayed suspension fluid/medium, pre-lysed cells from all cultures for Ambient results could be very important in the treatment of infected and chronic wounds which are often hypoxic. The
ATP concentration and lysis solution were lysed to determine total ATP results suggest a combination treatment of Silver and high levels of oxygen may perform better as an
concentration. antimicrobial than silver alone. More studies are needed to determine clinical results and with other wound
pathogens.