Disinfecting non-critical medical equipment – Effectiveness of hydrogen peroxide dry mist as an adjunctive method

Enrica Amodio 1), Stefan P. Kuster 1), Christian Garzoni 2), Annelies S. Zinkernagel 1), Hugo Sax 1), Aline Wolfensberger 1)
1) Division of Infectious Diseases and Hospital Epidemiology, University Hospital Zurich, University of Zurich, Zurich, Switzerland
2) Division of Internal Medicine and Infectious Disease, Clinica Moncucco , Lugano, Switzerland


Non-critical medical items, i.e. medical equipment and environmental surfaces, are often colonized by pathogens and contribute to pathogen transmission if not cleaned properly. As manual disinfection is prone to failure, a standardized, nonoperator dependent additional disinfection might work as «safety net». We aimed to test the effectiveness of one cycle of dry mist of hydrogen peroxide (DMHP) nebulization in reducing bacterial burden on «ready to use» non-critical objects.


A programmable device (HyperDRYMist®, Modulator Micro-Nebulizer 99MB by 99Technologies, Switzerland) generating a dry mist of hydrogen peroxide was used in a 60m3 closed (but unsealed) room. Swab samples of 16 different types of «ready to use» (i.e. disinfected according to USZ guidelines) objects were taken before and after nebulization. For the comparison of the bacterial burden in colony forming units (CFU) before and after nebulization, we excluded the following objects from analysis: 1) Objects with zero CFU before nebulization, 2) objects with CFU count before nebulization too numerous to count, and 3) objects with higher CFU count after nebulization than before. Objects were defined as «clean» according to Dancer et al.: clean < 500CFU/100cm2.


Of all included 160 objects, a median of 13.7 CFU/100cm2 (range 0.0-12’500.0) was found before nebulization. The highest median bacterial burden was found on remote controls (168.0 CFU/100 cm2, range: 4.0-1000.0), the lowest median bacterial burden was found on wheelchairs (0.0 CFU/100 cm2, range: 0.0-113.0). Only skin and environmental flora was detected.

Bacterial burden before and after nebulization

Median CFU before and after nebulization

  • – 82.4% overall mean CFU decrease by nebulization
  • – 64.2% of objects had a CFU decrease of > 90%
  • – 100% of objects were «clean» (i.e. < 500 CFU/100 cm2) after nebulization
  • – 59.4% of objects showed no bacterial growth after nebulization


Using DMHP results in a decrease of bacterial burden on «ready to use» non-critical objects. This might help to prevent the transmission of pathogens between patients. DMHP is a standardised, automatized and non-manual disinfection-method, that for example could be used on high-risk wards or during outbreaks.

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