Alternative Room Disinfection Modalities –Pros and Cons - Use of Biocidal Surfaces for Reduction of Healthcare Acquired Infections - page 191

Table 9.1 Definitions of efficacy, effectiveness, and efficiency
Efficacy Did the agent work under controlled conditions such as in the laboratory?
Effectiveness Did the agent work as intended in field conditions? This category included safety
of the product for humans, laboratory animals, environmental surfaces
or equipment

Efficiency If the agent was determined to be effective, does the benefit exceed the cost? It is

important to note that efficacy and effectiveness must be demonstrated before
efficiency should be considered

The EPA reviewed the results of four models of fumigation equipment for their
ability to destroy three types of spore forming bacteria [ 80 ]. The bacteria were:
Bacillus anthracis Ames strain ( B. anthracis ), Bacillus subtilis ( B. subtilis ), and
Geobacillus stearothermophilus ( G. stearothermophilus ). Test strips of seven types
of porous (e.g., carpet) and non-porous (e.g. galvanized metal) materials were
treated with a concentration of 10 8 viable biological spores. Two approaches used
chlorine dioxide as a fumigant, one used formaldehyde, and one used hydrogen
peroxide plasma. The Sabre Technical Services system generated 3,000 ppm of
chlorine dioxide in a 3 h treatment. The CDG Research Corporation system was
designed to release 2,000 ppm of chlorine dioxide over a 6 h period. The CERTEK,
Inc. formaldehyde generator had an average concentration of 1,100 ppm over an
11 h period. The BIOQUELL, Inc. hydrogen peroxide plasma generator achieved a
1,000 ppm concentration in a 1 h cycle. The EPA published tests provided for
“worst-case” scenarios for fumigation treatment because it is more difficult to
destroy surface contamination than spores dispersed in the air [ 57 ]. The EPA
tests of sporicidal efficacy found significant differences depending on the type of
surface, the type of microbial spore, and the type of fumigant. As expected, all
fumigants performed better on non-porous materials, and industrial grade carpet
proved most difficult to decontaminate. In general, chlorine dioxide and formalde-
hyde performed better than hydrogen peroxide plasma in destroying spores.
For example, the Sabre Technical Services chlorine dioxide generator achieved a
greater than 7.0 log kill of spores in carpeting, whereas the BIOQUELL Inc.
hydrogen peroxide generator had only a 0.81 log reduction.
While hydrogen peroxide was found to be less effective in the destruction
of bacterial spores, French et al., found it to be more effective than conven-
tional cleaning in destroying MRSA in rooms previously occupied by patients
carrying this organism [ 37 ]. After treating these rooms for 40 min at a concentra-
tion of 500 ppm, they found that MRSA had been destroyed in 84 of 85 locations
tested. They also reported the destruction of test samples containing 10 6
G. stearothermophilus spores that were applied to some stainless steel disks
suspended in the room. Krause et al., had similar success with hydrogen peroxide
in decontaminating animal research laboratory areas [ 76 ]. They used the VHP1000
system for hydrogen peroxide fumigation of animal rooms, and this unit was
designed for direct connection to cages and rooms. Also, due to the design of the
rooms, work could be continued in adjacent rooms or areas. The machine opera-
tional cycle lasted 3 h and outside monitoring of concentrations of hydrogen