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The presence of Methicillin resistant Staphylococcus aureus (MRSA) within chronic wounds poses a risk to the patient and surrounding patients/carers. Sequestration of MRSA in a dressing could improve the infection status of the wound bed and decrease the risk of MRSA transmission.
This study assesses MRSA sequestration in superabsorbent (SAP) dressings following absorption.
Methods
Five different SAP dressings were assessed over 7 days compared to knotted gauze. Dressings (n=12) were placed on top of 15ml of MRSA inoculum containing 106 cfuml-1. 15ml of inoculum was added daily for 7 days to simulate a highly exuding wound.
On days 1, 3 and 7 dressings were transferred to agar plates and incubated overnight at 37˚C. Dressings were then removed, and the plates photographed for evidence of MRSA transfer from the dressing.
Samples of the inner material of each dressing were processed and remaining viable bacteria quantified. Additional samples of the inner core were fixed and visualised using Environmental Scanning Electron Microscopy (ESEM).
Results
Each dressing was able to uptake the full volume of MRSA inoculum supplied over the 7 days. The Gauze control was unable to handle the fluid. Subsequently, the SAP dressings retained significantly more bacteria than gauze (average 1 log improvement) (p<0.001). One dressing demonstrated a 4 log improvement in bacterial retention.
On transfer to agar, a range of bacterial transfer was seen, some dressings demonstrated little to no transfer with others allowing growth at each time point.
ESEM imaging showed one dressing contained no viable MRSA, three displayed MRSA on the surface, and one held MRSA beneath the gelling agent.
Conclusion
A range of sequestration abilities were observed throughout the test. All SAP dressings demonstrated an improvement over gauze. One dressing demonstrated increased sequestration, displaying no viable bacteria on ESEM imaging, and a 4 log improvement over gauze.