Comparative Surface Microbial Contamination of a Cardboard Spacer MDI PLUS® and Conventional Plastic Inhalation Devices under Simulated Repeated Use

Background Pressurized metered-dose inhalers and spacer devices repeatedly come in contact with the mouth, raising concerns regarding microbiological contamination during routine use. Limited data compares microbial contamination across different spacer materials under simulated real-world handling and storage conditions.Methods We quantified external and internal-surface bioburden (CFU/cm2) on the plastic AeroChamber Plus® valved holding chamber, plastic pMDI mouthpieces, and the cardboard MDI PLUS® spacer at baseline and after a standardized use protocol of 20 actuations (4 actuations/day for 5 days) followed by 7 days of ambient storage. Testing was performed with salbutamol (100 µg), beclometasone (250 µg), and a beclometasone/salbutamol combination (250/100 µg). Organisms were cultured on selective media and identified by standard biochemical assays and Analytical Profile Index (API).Results Across all formulations and time points, the cardboard MDI PLUS® spacer consistently showed lower recoverable surface microbial contamination compared with the plastic devices (AeroChamber Plus® and pMDI mouthpiece). Gram-negative organisms, including Pseudomonas spp., were detected on plastic spacers and pMDI mouthpieces but were not recovered from the cardboard spacer under any condition. Total microbial counts on plastic devices ranged from approximately 40 - 48 CFU/cm2, whereas counts on the cardboard spacer remained lower, ranging from approximately 22 - 26 CFU/cm2. Candida albicans was detected on plastic devices, but was not recovered from the cardboard spacer following repeated use and storage in some formulations.Conclusions Under simulated repeated use, the cardboard-based spacer exhibited lower recoverable surface microbial contamination than the conventional plastic inhalation devices. These data highlight the potential influence of device material on microbial retention and may inform device selection and hygiene practices in routine respiratory care.