Hydrogen peroxide vapour vs. aerosol

Jon Otter (@jonotter) Disinfection , ,

q-10vsasp4

There has been an awful lot of discussion out in the field about various hydrogen peroxide systems used for “no-touch” automated room disinfection. Comparison of different systems through assessment of individual studies is tricky because different methods are used to assess the effectiveness of the products. Thus, the only way to get an accurate comparison of different technologies is through head-to-head comparisons.

A recently published study compared a hydrogen peroixde vapour (HPV) system (Bioquell) with an aerosolised hydrogen peroxide (aHP) system (ASP Glosair). The independent study was performed by researchers at St. Georges’ Hospital Testing was performed in a 50m3 room with a 13m3 anteroom, representing a single occupancy room with bathroom. For both systems it was found that rooms must be sealed to prevent leakage and room re-entry must be led by a hand held sensor to ensure safety. HPV generally achieved a 6-log reduction of spore BIs and in-house prepared test discs inoculated with MRSA, Clostridium difficile and Acineotbacter baumannii, whereas aHP generally achieved a 4-log reduction or less. The aHP system had reduced efficacy against the catalase-positive A. baumannii with a <2-log reductions in the majority of room locations. HPV was able to penetrate soiling more effectively than aHP and uneven distribution of the active agent within the enclosure was evident for aHP but not for HPV.

It is difficult to produce a laboratory challenge that is truly representative of field conditions, but the authors did a thorough job and used several different ways to measure the efficacy of the products, concluding that ‘the HPV system was safer to operate, slightly faster and achieved a greater level of biological inactivation than the aHP system.’

Article citation: Fu TY, Gent P, Kumar V. Efficacy, efficiency and safety aspects of hydrogen peroixde vapour and aerosolized hydrogen peroixde room disinfection systems. J Hosp Infect 2012; 80: 199-205.

Do biofilms on dry hospital surfaces change how we think about hospital disinfection?

Jon Otter (@jonotter) Biofilm , , ,

An important paper published in the Journal of Hospital Infection has identified biofilms on dry hospital surfaces. Biofilms are known to be important in several areas of medicine including indwelling medical devices and endoscope tubing, usually associated with surface-water interfaces. However, it was unclear whether biofilms formed on dry hospital surfaces. The study by Vickery et al. ‘destructively sampled’ several hospital surfaces after cleaning and disinfection using bleach (i.e. cut the materials out of the hospital environment and took them to the lab for analysis). Scanning electron microscopy was used to examine the surfaces for biofilms, which were identified on 5/6 surfaces: a curtain, a blind cord, a plastic door, a wash basin and a reagent bucket. Furthermore, MRSA was identified in the biofilm on three of the surfaces.

biofilm

Could it be that we have missed or underestimated the importance of biofilms on dry hospital surfaces? Biofilms could explain why vegetative bacteria can survive on dry hospital surfaces for so long, be part of the reason why they are so difficult to remove or inactivate using disinfectants (bacteria in biofilms can be 1000x more difficult to kill than corresponding planktonic bacteria) and explain to some degree the difficulty in recovering environmental pathogens by surface sampling.

Biofilms are clearly not the only reason for failures in hospital disinfection given the difficulty in achieving adequate distribution and contact time using manual methods, but these findings may have implications for infection control practices within hospitals and on the choice of the appropriate disinfectants used to decontaminate surfaces.

Article citation: Vickery K, Deva A, Jacombs A, Allan J, Valente P, Gosbell IB. Presence of biofilm containing viable multiresistant organisms despite terminal cleaning on clinical surfaces in an intensive care unit. J Hosp Infect 2012; 80: 52-55.

Image courtesy of the Lewis Lab at Northeastern University. Image created by Anthony D’Onofrio, William H. Fowle, Eric J. Stewart and Kim Lewis