Introduction and objectives Klebsiella pneumoniae (KPN) is an opportunistic pathogen for patients with chronic pulmonary disease. In-use single time-point sampling of valved holding chamber spacer (VHC) bodies has shown evidence (Cohen and Cohen, JAMA 2003, 290:195–196) of bacterial contamination particularly with Pseudomonas species and Klebsiella. We are not aware of multi time-point bacterial survival research and, accordingly, have assessed in vitro two plastic VHC body materials which are in common use in the UK.

Methods Test pieces, in n = 5 sub-group samples (Samples), of polystyrene (sterile Control) and of VHC bodies of AeroChamber Plus, Trudell Medical International (ACP) and A2A Spacer, Clement Clarke International Ltd. (A2A) were equilibrated for 24 h at 20°C/65% relative humidity (RH). Samples were inoculated with 100 muL distilled-water aliquots of KPN 3.6 × 10⁶ cells.mL^-1 and incubated at 20°C in 65% RH chambers. KPN surface survival was measured at 0, 24, 48 and 72 h time-points using a method based on ISO Standard 22196:2007 (Askew, Efficacy Assessment of Treated Articles: A Guidance, February 2014 http://dx.doi.org/10.6027/NA2014–904) and total viable count enumerated. 72 h data (Log₁₀ Colony Forming Units (CFU).cm^-2) were analysed using one-way analysis of variance.

Results Geometric mean CFU.cm^-2 data are given in the table. Control and ACP KPN populations declined to the 48 h time-point, thereafter increasing (Control) and remaining constant (ACP). A2A KPN population showed a constant decline, with no re-growth. At 72 h, Log₁₀ CFU KPN data for A2A were significantly smaller (p < 0.05) compared to ACP (-0.47 difference, 95% CI -0.81 to -0.13) and to Control (0.74 difference, 95% CI 0.41 to 1.08).

Conclusions We interpret the 72 h increase in Control KPN as the outcome of the initial decline creating dead cell matter that acted as a nutrient source. The stability (ACP) and significant decline (A2A) in KPN is therefore an interesting finding. We subscribe the latter to the presence of an antimicrobial additive in the body polymer material. The clinical implications of these findings are relevant to VHC hygiene and patient health, and require further investigation.