Aspergillus fumigatus in valved holding chambers: use of silver ion additive technology on fungal activity and aerosol delivery characteristics

Sanders MJ, Bruin R, Tran CH

Valved holding chambers (VHCs) are an essential auxiliary device for pressurised metered dose inhalers (pMDIs). However, VHCs are capable of hosting fungi, thereby possibly promoting pulmonary aspergillosis via contaminated devices. VHC-polymers incorporating silver ions have been shown to resist the growth of certain microbes. The present research examined the in vitro effects on (i) the spored activity of Aspergillus fumigatus and (ii) the aerosol particle size distribution (APSD) and dose characteristics of salbutamol (Ventolin® Evohaler® pMDI) from the VHC Able Spacer® 2 with either ~1wt% (the standard commercially-available device) or 4wt% silver ions incorporated. Fungal activity was determined using a modified ISO 22196:2011 methodology for contaminant splashes onto non-porous surfaces, using flat discs of ~1% and 4% silver ion polymer material. APSD was determined from standard Next Generation Impactor (NGI) testing. Fungal activity of A. fumigatus was reduced at 24h when silver ions were present, compared to Control, and there was a five-fold Log10 difference between the ~1% and 4% silver ion material. There were no differences in salbutamol aerosol characteristics and APSD delivered via the standard Able Spacer 2 (~1% silver ions) and the test Able Spacer 2 (4% silver ions). The increase in silver ions did not alter the performance of the Ventolin pMDI. In vivo, the connection between VHC contamination and infection, and the aerosolisation of chamber contaminants remain unanswered. However, the availability of a new spacer with enhanced silver ion concentration for at-risk patients could extend the potential for prevention of concomitant fungal lung disease.

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