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Survival of Bacterial Species on Drywall
and Wood Treated with "Microbial Shield"
Absar
Alum, Ph.D.
Department of Civil and Environmental Engineering
Arizona State University
Tempe, AZ 85287-5306
A Brief Report Prepared for
Global Prevention Services
Scottsdale, AZ 85260
January 10, 2005
INTRODUCTION
The test material consisting of two sets
of drywall and wood coupons (3”x3”) treated with Microbial Shield were proved
by Global Prevention Services (GPS), Scottsdale, Arizona, for antibacterial
performance evaluation. The control material, which included two sets of
non-treated drywall and wood coupons were also provided by GPS. These
non-treated coupons were included in the experimental plan as negative
controls. The bacterial challenge studies were conducted at the National
Science Foundation Water Quality Center at Arizona State University to
verify the bacterial inactivation capabilities of the drywall and wood
sample treated with “Microbial Shield”. The test material was evaluated against
Escherichia, Bacillus, and Salmonella, which are commonly found in
water-damaged construction material samples. The objective of this study was
to verify the proof of concept for bacterial inactivation capabilities of
the proprietary product “Microbial Shield” applied on wood and drywall.
MATERIAL AND METHODS
The bacterial species tested in this
study were E. coli, Bacillus subtilis, and Salmonella
typhimurium. The standard procedures (Standard Methods for the
Examination of Water and Wastewater, 19th Edition) were followed
for bacterial culture maintenance, propagation, and inoculated with high
numbers (~108) of each of the bacterial species. Control samples
(non-treated) for both drywall and wood were also inoculated with same
number of test bacterial species. Experiment and control ample were
incubated under similar conditions for 15 days. Test and control samples
were periodically removed from incubation chamber and assayed from the
respective bacterial species. Bacteria were recovered from sample coupons
using glycine buffered and assayed using membrane filtration.
RESULTS
An independent series of experiments
were conducted with the bacteria E. coli, Bacillus
subtilis, and Salmonella typhimurium. The result of the time course study of survival of test bacterial species on
drywall and wood samples treated with “Microbial Shield” are presented in
Figure 1 and 2. Approximately 100 million cells of E. coli, Bacillus
subtilis, and Salmonella typhimurium were inoculated on test and control
samples, and no test bacteria were recovered from treated wood or drywall
sample after 24 hour. The treated samples remained negative for three test
bacteria throughout the course of this study (Figure 1 and 2). However, test
bacterial species survived on control samples of drywall and wood and were
recovered for almost a week. The data suggests that E.
coli, Bacillus subtilis, and Salmonella typhimurium cells are rapidly inactivated on drywall and wood treated with Microbial
Shield. It is important to note that the observations are based on
small-scale experiment for proof of concept.
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