A COMPARATIVE EVALUATION OF METHODS FOR DETERMINING THE BACTERIAL CONTAMINATION OF SURFACES a

In order to meet planetary-protection requirements, culturable bacterial spore loads are measured representatively for the total microbial contamination of spacecraft. However, the National Aeronautics and Space Administration's (NASA's) cotton swab protocols for spore load determination have not changed for decades. To determine whether a more efficient alternative was available, a novel swab was evaluated for recovery of different Bacillus atrophaeus spore concentrations on stainless steel and other surfaces. Two protocols for the nylon-flocked swab (NFS) were validated and compared to the present NASA standard protocol. The results indicate that the novel swab protocols recover 3-to 4-fold more (45.4% and 49.0% recovery efficiency) B. atrophaeus spores than the NASA standard method (13.2%). Moreover, the nylon-flocked-swab protocols were superior in recovery efficiency for spores of seven different Bacillus species, including Bacillus anthracis Sterne (recovery efficiency, 20%). The recovery efficiencies for B. atrophaeus spores from different surfaces showed a variation from 5.9 to 62.0%, depending on the roughness of the surface analyzed. Direct inoculation of the swab resulted in a recovery rate of about 80%, consistent with the results of scanning electron micrographs that allowed detailed comparisons of the two swab types. The results of this investigation will significantly contribute to the cleanliness control of future life detection missions and will provide significant improvement in detection of B. anthracis contamination for law enforcement and security efforts.

Section: Discussionmentioning

confidence: 99%

Section: Discussionmentioning

confidence: 99%

Validation of a Nylon-Flocked-Swab Protocol for Efficient Recovery of Bacterial Spores from Smooth and Rough Surfaces

Probst

Facius

Wirth

et al. 2010

“…Studies have also shown that a significant proportion of the biological agent that can be sampled from a solid surface remains adhered to the sampling materials despite efforts to wash it off for testing or is lost during the sample processing (1,7,19).…”

mentioning

confidence: 99%

Surface Sampling of Spores in Dry-Deposition Aerosols

Edmonds

Collett

Valdes

et al. 2009

108

The ability to reliably and reproducibly sample surfaces contaminated with a biological agent is a critical step in measuring the extent of contamination and determining if decontamination steps have been successful. The recovery operations following the 2001 attacks with Bacillus anthracis spores were complicated by the fact that no standard sample collection format or decontamination procedures were established. Recovery efficiencies traditionally have been calculated based upon biological agents which were applied to test surfaces in a liquid format and then allowed to dry prior to sampling tests, which may not be best suited for a real-world event with aerosolized biological agents. In order to ascertain if differences existed between air-dried liquid deposition and biological spores which were allowed to settle on a surface in a dried format, a study was undertaken to determine if differences existed in surface sampling recovery efficiencies for four representative surfaces. Studies were then undertaken to compare sampling efficiencies between liquid spore deposition and aerosolized spores which were allowed to gradually settle under gravity on four different test coupon types. Tests with both types of deposition compared efficiencies of four unique swabbing materials applied to four surfaces with various surface properties. Our studies demonstrate that recovery of liquid-deposited spores differs significantly from recovery of dry aerosol-deposited spores in most instances. Whether the recovery of liquid-deposited spores is overexaggerated or underrepresented with respect to that of aerosol-deposited spores depends upon the surface material being tested.Since 2001, the biological defense community has made great strides in improving our readiness to respond to and recover from an attack with a biological pathogen. Lessons learned in restoring operations within large building complexes contaminated with Bacillus anthracis spores or ricin toxin have led to the development of more-efficient tools for the detection of biological pathogens and means of decontaminating affected facilities. A key step in determining the extent of contamination during the initial stages of a bioterrorist attack and in ascertaining if a building can be reoccupied in the final stages of cleanup is our ability to effectively sample an area and deliver a specimen for testing.Currently there are several commercially available sampling products (2,3,8,9,16,23), but test data demonstrate that they are limited in their ability to detect and recover biological samples, with estimated recovery efficiencies ranging from approximately 10% to 40% (8,11,19). Studies have also shown that a significant proportion of the biological agent that can be sampled from a solid surface remains adhered to the sampling materials despite efforts to wash it off for testing or is lost during the sample processing (1,7,19).Historically, recovery efficiencies of swabs found in sampling kits have been calculated based on their ability to recover a liquid bacterial...

“…Recovery, enumeration, and identification of microorganisms on surfaces have been a focus of scientific inquiry for over a century, with initial applications primarily related to food safety (2), the integrity of the National Aeronautics and Space Administration (NASA) programs (35), and hygiene in domestic (22,50) and clinical (1,6,19) settings. However, the reliability of traditional surface sampling methods came under intense scrutiny in 2001 following the widespread contamination of multiple large building complexes with spores identified as Bacillus anthracis, the causative agent of anthrax.…”

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confidence: 99%

Impact of Processing Method on Recovery of Bacteria from Wipes Used in Biological Surface Sampling

Downey

Silva

Olson

et al. 2012

ABSTRACTEnvironmental sampling for microbiological contaminants is a key component of hygiene monitoring and risk characterization practices utilized across diverse fields of application. However, confidence in surface sampling results, both in the field and in controlled laboratory studies, has been undermined by large variation in sampling performance results. Sources of variation include controlled parameters, such as sampling materials and processing methods, which often differ among studies, as well as random and systematic errors; however, the relative contributions of these factors remain unclear. The objective of this study was to determine the relative impacts of sample processing methods, including extraction solution and physical dissociation method (vortexing and sonication), on recovery of Gram-positive (Bacillus cereus) and Gram-negative (Burkholderia thailandensisandEscherichia coli) bacteria from directly inoculated wipes. This work showed that target organism had the largest impact on extraction efficiency and recovery precision, as measured by traditional colony counts. The physical dissociation method (PDM) had negligible impact, while the effect of the extraction solution was organism dependent. Overall, however, extraction of organisms from wipes using phosphate-buffered saline with 0.04% Tween 80 (PBST) resulted in the highest mean recovery across all three organisms. The results from this study contribute to a better understanding of the factors that influence sampling performance, which is critical to the development of efficient and reliable sampling methodologies relevant to public health and biodefense.