A recent Health Protection Scotland study showed the mean time to achieve MRSA decolonisation of 10 days to be substantially longer than the average length of stay of 3-4 days for all colonised patient admissions. With only 3.1% of patients in the study completing decolonisation therapy, together with the reported high rate of treatment failure and relapse, a review of the current decolonisation guidelines is warranted. The aim of this pilot study was to develop a model to test the efficacy of mupirocin treatment of MRSA biofilms. A standard microtitre plate method and a flow cell system were used to assess the efficacy of mupirocin in the eradication of MRSA biofilms. Bacterial cell death was determined using the metabolic dye resazurin and validated by visualisation of the biofilm using LIVE/DEAD® BacLight™ viability stain and confocal scanning laser microscopy (CSLM). Six biofilm forming hospital acquired MRSA isolates all showed planktonic minimum inhibitory concentrations (MIC) of 0.12µg/ml. After overnight exposure of biofilms to mupirocin at 1 x, 4 x, 10 x and 100 x MIC using the microtitre plate model, 59%, 55%, 52% and 46% of cells survived respectively. Following treatment with the clinically prescribed concentration of 2% mupirocin (166 x MIC) 39% of cells remained viable. Using a flow cell system, cell survival was down 46% after exposure to 2% mupirocin for just 30 minutes, representative of current treatment. Biofilm imaging after LIVE/DEAD staining confirmed that half of the cells remained viable. This pilot study has demonstrated the utility of an enclosed flow cell system for the monitoring of antibiotic mediated cell death within a biofilm and provides evidence for the use of the model in future experiments to re-evaluate the effectiveness of repeated dosing representative of current prescribing regimes with an aim to improving the effectiveness of MRSA decolonisation therapy.
|Publication status||Published - 19 Nov 2012|
- MRSA screening
- nasal decolonisation
- Health Protection Scotland