A proof of concept evaluation of dry heat as an aerial disinfection method for hospitals: preliminary data for bactericidal efficacy

Background

In hospitals, the prevention of healthcare-associated infections requires biocleaning of the patient's immediate environment. Micro-organisms can survive for long periods of time – up to several months – on certain environmental surfaces, resulting in their transmission to the patient through direct contact or via the hands of healthcare workers. Dry heat is a long-recognized antimicrobial process. However, its use as an aerial method of disinfection for hospital surfaces is innovative. An evaluation of bactericidal efficacy is required before any real-world application, to ensure that this method satisfies current standards.

Aim

In this study, we aimed to investigate the effect of dry heat generated at a temperature of 60 °C for 30 min on the bacterial contamination of horizontal surfaces in a room, comparing this method with disinfection by the direct application of a detergent-disinfectant – the current reference method.

Methods

Four supports, made from the materials most commonly found in patient rooms, were inoculated with five different bacterial species representative of hospital ecology and tested. More than 900 bacteriological samples were taken at different times after the disinfection phase.

Findings

The bactericidal activity of the dry heat process was demonstrated by a decrease in bacterial levels of more than 5 log₁₀ cfu/mL in 10 min, regardless of bacterial species or substrate. After 30 min, dry heat was significantly more effective than detergent-disinfectant and mechanical action alone.

Conclusion

Dry heat (60 °C for 30 min) showed bactericidal activity against non-spore-forming vegetative bacteria under the conditions tested in this study. This method can be automated, meets ecological criteria and is not toxic to humans; it may represent a potential alternative for surface disinfection using quaternary ammonium disinfectants against vegetative bacteria, although further investigation is required to confirm efficacy against other clinically relevant pathogens.