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J Appl Microbiol. 2018 May;124(5):1092-1106. doi: 10.1111/jam.13706. Epub 2018 Mar 13.

Comparison of false-negative rates and limits of detection following macrofoam-swab sampling of Bacillus anthracis surrogates via Rapid Viability PCR and plate culture.

Author information

1
National Security Directorate, Pacific Northwest National Laboratory, Richland, WA, USA.

Abstract

AIMS:

We evaluated the effects of Bacillus anthracis surrogates, low surface concentrations, surface materials and assay methods on false-negative rate (FNR) and limit of detection (LOD95 ) for recovering Bacillus spores using a macrofoam-swab sampling procedure.

METHODS AND RESULTS:

Bacillus anthracis Sterne or Bacillus atrophaeus Nakamura spores were deposited over a range of low target concentrations (2-500 per coupon) onto glass, stainless steel, vinyl tile and plastic. Samples were assayed using a modified Rapid Viability-PCR (mRV-PCR) method and the traditional plate culture method to obtain FNR and LOD95 results.

CONCLUSIONS:

Mean FNRs tended to be lower for mRV-PCR compared to culturing, and increased as spore concentration decreased for all surface materials. Surface material, but not B. anthracis surrogate, influenced FNRs with the mRV-PCR method. The mRV-PCR LOD95 was lowest for glass and highest for vinyl tile. LOD95 values overall were lower for mRV-PCR than for the culture method.

SIGNIFICANCE AND IMPACT OF STUDY:

This study adds to the limited data on FNR and LOD95 for mRV-PCR and culturing methods with low concentrations of B. anthracis sampled from various surface materials by the CDC macrofoam-swab method. These are key inputs for planning characterization and clearance studies for low contamination levels of B. anthracis.

KEYWORDS:

Bacillus spores; PCR (polymerase chain reaction); false-negative rate; limit of detection; macrofoam-swab sampling; plate culture

PMID:
29356220
DOI:
10.1111/jam.13706
[Indexed for MEDLINE]

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