Evaluation of swabs and transport media for the recovery of Yersinia pestis

• Published in: Journal of microbiological methods 2014-01, Vol.96, p.35-41
• Main Authors: Gilbert, Sarah E., Rose, Laura J., Howard, Michele, Bradley, Meranda D., Shah, Sanjiv, Silvestri, Erin, Schaefer, Frank W., Noble-Wang, Judith
• Format: Article
• Language: English
• Subjects: Bacillus anthracis; Buffers; Environmental Microbiology; Humans; Preservation, Biological - methods; Recovery; Specimen Handling - methods; Swab; Temperature; Time Factors; Transport media; Yersinia pestis; Yersinia pestis - isolation & purification
• ISSN: 0167-7012; 1872-8359
• DOI: 10.1016/j.mimet.2013.10.017

The Government Accountability Office report investigating the surface sampling methods used during the 2001 mail contamination with Bacillus anthracis brought to light certain knowledge gaps that existed regarding environmental sampling with biothreat agents. Should a contamination event occur that involves non-spore forming biological select agents, such as Yersinia pestis, surface sample collection and processing protocols specific for these organisms will be needed. Two Y. pestis strains (virulent and avirulent), four swab types (polyester, macrofoam, rayon, and cotton), two pre-moistening solutions, six transport media, three temperatures, two levels of organic load, and four processing methods (vortexing, sonicating, combined sonicating and vortexing, no agitation) were evaluated to determine the conditions that would yield the highest percent of cultivable Y. pestis cells after storage. The optimum pre-moistening agent/transport media combination varied with the Y. pestis strain and swab type. Directly inoculated macrofoam swabs released the highest percent of cells into solution (93.9% recovered by culture) and rayon swabs were considered the second best swab option (77.0% recovered by culture). Storage at 4°C was found to be optimum for all storage times and transport media. In a worst case scenario, where the Y. pestis strain is not known and sample processing and analyses could not occur until 72h after sampling, macrofoam swabs pre-moistened with PBS supplemented with 0.05% Triton X-100 (PBSTX), stored at 4°C in neutralizing buffer (NB) as a transport medium (PBSTX/NB) or pre-moistened with NB and stored in PBSTX as a transport medium (NB/PBSTX), then vortexed 3min in the transport medium, performed significantly better than all other conditions for macrofoam swabs, regardless of strain tested (mean 12 – 72h recovery of 85.9–105.1%, p