Parameters Affecting Spore Recovery from Wipes Used in Biological Surface Sampling

Abstract

The need for the precise and reliable collection of potential biothreat contaminants has motivated research in developing a better understanding of the variability in biological surface sampling methods. In this context, the objective of this work was to determine parameters affecting the efficiency of extracting Bacillus anthracis Sterne spores from commonly used wipe sampling materials and to describe performance using the interfacial energy concept. In addition, surface thermodynamics was applied to understand and predict surface sampling performance. Wipe materials were directly inoculated with known concentrations of B. anthracis spores and placed into extraction solutions, followed by sonication or vortexing. Experimental factors investigated included wipe material (polyester, cotton, and polyester-rayon), extraction solution (sterile deionized water , and physical dissociation method (vortexing or sonication). The most efficient extraction from wipes was observed for solutions containing the nonionic surfactant Tween 80. The increase in extraction efficiency due to surfactant addition was attributed to an attractive interfacial energy between Tween 80 and the centrifuge tube wall, which prevented spore adhesion. Extraction solution significantly impacted the extraction efficiency, as determined by statistical analysis (P < 0.05). Moreover, the extraction solution was the most important factor in extraction performance, followed by the wipe material. Polyester-rayon was the most efficient wipe material for releasing spores into solution by rank; however, no statistically significant difference between polyester-rayon and cotton was observed (P > 0.05). Vortexing provided higher spore recovery in H 2 O and H 2 O-T than sonication, when all three wipe materials and the reference control were considered (P < 0.05).The successful collection of biological contaminants from surfaces is critical to gaining insight into the environmental conditions in which we live and work as well as to ensure public safety in times of biothreat incidents. Traditional methods for biological sample collection have focused on assessing bacterial contamination on surfaces relevant to environmental, clinical, and food safety settings, in which case swabs were the most common adsorptive materials used for sample collection (6,20,21,23,24,29,35,38). Since the anthrax attacks in 2001, sampling methods using wipe and vacuum collection devices have been developed to meet the needs of a broader range of applications, including building characterization and clearance. Data accumulated from sampling of contaminated facilities in 2001 using HEPA vacuum, dry and premoistened swab, and wipe sampling methods demonstrated that sampling efficiency was dependent on surface sampling techniques and sample collection conditions (42,47).Overall recovery efficiency is sensitive to the applied experimental conditions due to a wide range of potential variables in surface sample collection methodologies, such as differences in extraction solution, adsorpti...

False-Negative Rate and Recovery Efficiency Performance of a Validated Sponge Wipe Sampling Method

“…Comparing our study's RE results to those from previous sampling studies is problematic because of many differences. The studies used a variety of sampling methods and materials (collection, extraction, analytical), surface materials, spore sizes and characteristics, and surface concentrations, and they were subject to different environmental conditions, each of which may affect REs (10,40). Using stainless steel as a test surface, the RE values from our study (which ranged from 36 to 63%, with an average of 52%) were larger than in other surface sampling studies.…”

“…The surface characteristics evaluated (including hydrophobicity, statics, contact angle, and porosity; unpublished data) did not show a relationship with RE, FNR, or LOD. However, surface chemistry effects were previously shown to influence REs of spores from sample media (10). In this study, the sampling and analysis methods were constant so that the effects of surface materials could be evaluated.…”

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

“…Three factors were evaluated for their impact on extraction efficiency: (i) organism, including one Gram-positive (B. cereus) and two Gram-negative cell types (B. thailandensis and E. coli), (ii) extraction solution, and (iii) physical dissociation method (PDM), including sonication, vortexing, or a combination thereof, for multiple time periods (Table 1). Extraction solutions and PDMs were chosen from those commonly found in the literature regarding extraction of biological agents from sampling materials (4,13,42,48). Inclusion of phosphate-buffered saline (PBS; pH 7.4) and Butterfield's buffer (BB; pH 7.2) allowed comparison of high-and low-salt solutions.…”

“…As a result, over the last decade needs for quantitative assessment capabilities have driven research on the relative effectiveness of different sampling processes as well as the development of validated surface sampling and sample processing methods (27,49). Notably, the vast majority of these studies have utilized B. anthracis spores (13,20,23,27,28,48) or spores of a surrogate organism (4,5,8,9,18,58). Comparatively little effort has been applied in recent years toward improved surface sampling of viruses (31) and vegetative bacterial cells that represent likely biothreat (BT) agents (or surrogates thereof) (7,29,39,60).…”

On importance of surface forces in a microfluidic fluidized bed

“…We attempted to better understand our Tween-80 related observations using the acidbase approach of van Oss, Chaudhury and Good (van Oss, 2008) in conjunction with the surface tension components of Da Silva et al (2011) for the hydrophobic tail and hydrophilic head of the Tween 80 molecule, which are summarised in Table 4. This analysis, which yields the interfacial energy estimates in Table 5, suggest that, when interacting with the glass particles, the Tween 80 molecules would prefer to attach via their tail.…”