Clearance sampling following an anthrax attack or other biological terror incident potentially requires samples to be collected from surfaces recently treated with decontaminant. The impact of residual decontaminant collected with samples also containing possible surviving pathogens was previously unknown.
Researchers from the U.S. Environmental Protection Agency (EPA) National Homeland Security Research Center have recently published study results examining the effects of decontaminant residues on the viability of Bacillus spores during wipe sample storage.
Two experimental approaches were used to determine if agent viability within wetted wipe samples (post-collection) is affected by the presence of pH- adjusted bleach residues, and therefore impacts the quantitative determination of Bacillus spore recovery.
Results indicated that following sample storage (22°C, overnight) the determined number of colony forming units (CFU) were not statistically different for positive controls and samples containing dry decontaminant residue.
The data supports the use of the current CDC- recommended wetted wipe procedures for sampling of dry non- porous surfaces following liquid-based surface decontaminations, as no effects on sample viability were observed when co-collected with dry pH-adjusted bleach residue.
“To reduce the risk of post-incident exposures, it is important that decisions regarding building clearance be based upon robust sampling and analysis procedures that are validated and well-characterized,” state the researchers. “These data are necessary for interpretation of post-bioterror or other contamination incident sampling results, and support current use of wetted wipes in non-porous surface sampling protocols for clearance following liquid decontamination activities.”
The researchers note that while the study fills an important knowledge gap in the surrounding the potential bias of post-decontamination sampling, the only decontaminant tested in this study was pH-adjusted bleach and that recoveries from porous surfaces, using other sampling methods may be different from these study results.
Read the full study as published in the open-access journal Biosafety: The Effects of Decontaminant Residue on the Viability of Bacillus Spores During Wipe Sample Storage.