Determination of the efficacy of two building decontamination strategies by surface sampling with culture and quantitative PCR analysis

Abstract

The efficacy of currently available decontamination strategies for the treatment of indoor furnishings contaminated with bioterrorism agents is poorly understood. Efficacy testing of decontamination products in a controlled environment is needed to ensure that effective methods are used to decontaminate domestic and workplace settings. An experimental room supplied with materials used in office furnishings (i.e., wood laminate, painted metal, and vinyl tile) was used with controlled dry aerosol releases of endospores of Bacillus atrophaeus ("Bacillus subtilis subsp. niger," also referred to as BG), a Bacillus anthracis surrogate. Studies were performed using two test products, a foam decontaminant and chlorine dioxide gas. Surface samples were collected pre- and posttreatment with three sampling methods and analyzed by culture and quantitative PCR (QPCR). Additional aerosol releases with environmental background present on the surface materials were also conducted to determine if there was any interference with decontamination or sample analysis. Culture results indicated that 10(5) to 10(6) CFU per sample were present on surfaces before decontamination. After decontamination with the foam, no culturable B. atrophaeus spores were detected. After decontamination with chlorine dioxide gas, no culturable B. atrophaeus was detected in 24 of 27 samples (89%). However, QPCR analysis showed that B. atrophaeus DNA was still present after decontamination with both methods. Environmental background material had no apparent effect on decontamination, but inhibition of the QPCR assay was observed. These results demonstrate the effectiveness of two decontamination methods and illustrate the utility of surface sampling and QPCR analysis for the evaluation of decontamination strategies.

FIG. 1.

Diagram of the experimental room. HEPA-filtered air is delivered into the room via two supply registers (S1 and S2) and exits through the return register (R). Sampling stands 1 to 5 support temperature and RH probes. Rectangles in the room represent sampling benches with wood laminate, metal, and vinyl tile surfaces.

FIG. 2.

Summary of culture results obtained for the detection of B. atrophaeus from surfaces in three experimental room trials before and after use of the foam decontaminant. Materials were contaminated by aerosolization of B. atrophaeus spores into the room, followed by settling of the bioaerosol onto surfaces in the room. Surface samples (929 cm² [1 ft²]) were collected with Heavy Wipes, swipes, and SSP kits prior to decontamination (pre-decon). Surfaces were treated with the foam and sampled postdecontamination (post-decon). All postdecontamination samples contained no culturable B. atrophaeus (lower detection limit range, 10 to 40 CFU per sample). Bar heights represent the mean (log₁₀) of three samples ± 1 SE.

FIG. 3.

Summary of QPCR results obtained for the detection of B. atrophaeus from surfaces before and after use of a foam decontaminant. Materials were contaminated by aerosolization of B. atrophaeus spores into the room, followed by settling of the bioaerosol onto surfaces. Surface samples (929 cm² [1 ft²]) were collected with Heavy Wipes, swipes, and SSP kits prior to decontamination (pre-decon). Surfaces were treated with the foam and sampled postdecontamination (post-decon). Bar heights represent the mean (log₁₀) of three samples ± 1 SE.

FIG. 4.

Summary of culture results obtained for the detection of B. atrophaeus from surfaces before and after decontamination with chlorine dioxide gas. Materials were contaminated by aerosolization of B. atrophaeus spores into the room, followed by settling of the bioaerosol onto surfaces. Surface samples (929 cm² [1 ft²]) were collected with Heavy Wipes, swipes, and SSP kits prior to decontamination (pre-decon). Surfaces were treated with chlorine dioxide gas and sampled postdecontamination (post-decon). Bar heights represent the mean (log₁₀) of three samples ± 1 SE.

FIG. 5.

Summary of QPCR results obtained for the detection of B. atrophaeus from surfaces before and after decontamination with chlorine dioxide gas. Materials were contaminated by aerosolization of B. atrophaeus spores into the room, followed by settling of the bioaerosol onto surfaces. Surface samples (929 cm² [1 ft²]) were collected with Heavy Wipes, swipes, and SSP kits prior to decontamination (pre-decon). Surfaces were treated with chlorine dioxide gas and sampled postdecontamination (post-decon). Bar heights represent the mean (log₁₀) of three samples ± 1 SE.