Mycobacterium tuberculosis is a major cause of morbidity and mortality worldwide and is becoming a greater concern due to the development of multidrug-resistant strains. M. tuberculosis can contaminate rooms, medical equipment, and research laboratories and has the propensity to be highly resistant to decontamination. The aim of this study was to determine the efficacy of room disinfection with a dry mist of hydrogen peroxide (DMHP) in a biosafety level 3 laboratory in the event of contamination with M. tuberculosis. The biological indicators (BIs) were comprised of presterilized cotton tissues on which amounts of about 10 7 CFU/ml of M. tuberculosis H37Ra were dried. The device (Sterinis; Gloster Sante Europe) provided a DMHP of 5% hydrogen peroxide during 25 min. Three experiments were performed. The viable bacteria were reduced by values of more than 5 log 10 , and no colony grew from any BI. In conclusion, DMHP shows promise as an effective and safe alternative to the currently used formaldehyde.Tuberculosis is a major public health problem, particularly with the development of multidrug-resistant strains (22). It was declared to be a global emergency by the World Health Organization (WHO) in 1993. Mycobacterium tuberculosis bacteria are most likely transmitted by aerosols and so can easily contaminate rooms in health care facilities or research laboratories. Moreover, these bacteria present high intrinsic resistance to disinfection and fumigation processes and possess effective defense mechanisms against oxidative stress (4, 5). Their resistance to disinfectants has been considered intermediate between those of other vegetative bacteria and spores. The components of the cell wall that are responsible for this high level of resistance are unknown, but both mycolic acids and arabinogalactan appear to be involved (3,20).Chemical liquids and vapors are mainly used as decontaminating agents. Traditional room fumigation has been conducted by using formaldehyde or ethylene oxide gas. These methods have been given up due to their toxicity and carcinogenicity. In June 2004, the International Agency for Research on Cancer (IARC) classified formaldehyde as carcinogenic for humans (6,12). It has been recommended in France since September 2006 that this substance not be used for room decontamination, and its production was definitively stopped in January 2007. Thus, research laboratories and hospitals must find other solutions for decontamination; H 2 O 2 provides an alternative to formaldehyde fumigation because of its biological efficacy against various microorganisms (7,8,11,13,17) and its safety (hydrogen peroxide readily decomposes to form water and oxygen).Hydrogen peroxide has already been recommended for the disinfection of a large variety of materials, including dental instruments (18) and bronchoscopes (2). The use of H 2 O 2 vapor (VHP) for the biodecontamination of biological safety cabinets (BSCs), rooms in health care facilities (8), ambulances (1), pharmaceutical facilities, and laboratories (10, 14, 15, ...

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