Evaluation and comparison of two Stuart's liquid swab transport systems tested by the CLSI M40 method

Investigations into Enhancing Yersinia pestis Cells Viability following Environmental Sampling for Forensic Analysis

Following an intentional or accidental bio-warfare agent (BWA) release, environmental sample analysis is absolutely critical to determine the extent of contamination. When dealing with nonspore forming BWA (e.g., Yersinia pestis), retention of cell viability is central to such analyses. Even though significant advances have been achieved in DNA sequencing technologies, a positive identification of BWAs in environmental samples must be made through the ability of cells to form colony-forming units upon culturing. Inability to revive the cells between collection and analysis renders such studies inconclusive. Commercial kits designed to preserve the viability of pathogens contained within clinical samples are available, but many of them have not been examined for their ability to preserve samples containing suspected BWAs. The study was initiated to examine the applicability of commercial solutions aiding in retention of Y. pestis viability in samples stored under nonpermissive temperatures, that is, 40 and 37°C. While none of the tested solutions sustained cell viability at 40°C, the results show five out of 17 tested preservatives were capable of supporting viability of Y. pestis at 37°C.

Evaluation of Commercial-off-the-Shelf Materials for the Preservation of Bacillus anthracis Vegetative Cells for Forensic Analysis

Environmental surface sampling is crucial in determining the zones of contamination and overall threat assessment. Viability retention of sampled material is central to such assessments. A systematic study was completed to determine viability of vegetative cells under nonpermissive storage conditions. Despite major gains in nucleic acid sequencing technologies, initial positive identification of threats must be made through direct culture of the sampled material using classical microbiological methods. Solutions have been developed to preserve the viability of pathogens contained within clinical samples, but many have not been examined for their ability to preserve biological agents. The purpose of this study was to systematically examine existing preservation materials that can retain the viability of Bacillus anthracis vegetative cells stored under nonpermissive temperatures. The results show effectiveness of five of seventeen solutions, which are capable of retaining viability of a sporulation deficient strain of B. anthracis Sterne when stored under nonrefrigerated conditions.

Evaluation of two types of swabs for sampling allograft musculoskeletal tissue

BACKGROUND

Allograft musculoskeletal tissue is commonly sampled by a swab for bioburden screening. To determine if bioburden recovery could be improved at the pre-analytical stage, two swab systems were evaluated: the Amies gel swab and the ESwab.

METHODS

In vitro studies were performed to determine the recovery of each swab system with <100 colony-forming unit of challenge organisms using inoculated swabs and by sampling inoculated femoral heads. The standard culture protocol used in this laboratory was also evaluated after sampling of inoculated femoral heads. A prospective study was performed with both swab systems used in parallel to sample cadaveric allograft musculoskeletal tissue.

RESULTS

The challenge organisms could be recovered from the in vitro inoculated studies. The standard culture protocol in this laboratory recovered all challenge organisms from both swab systems. One hundred and six paired Amies and ESwabs were collected from eight cadaveric donors with skin commensals the predominant isolates.

CONCLUSIONS

The sampling of an inoculated femoral head was included to reflect routine swab sampling practice as was the inclusion of the standard method used in this laboratory. This appears to be the first study to compare Amies gel swabs with ESwabs to sample allograft femoral heads and in a prospective study with cadaveric allograft musculoskeletal tissue. Other comparative studies of swab systems have used a much higher inoculum to mimic an infection; however, sepsis is an exclusion criterion for allograft donors. It was found that the Amies gel swab and ESwab are both suitable sampling devices for bioburden testing of allograft musculoskeletal tissue.

Survival of methicillin-resistant Staphylococcus aureus and vancomycin-resistant Enterococcus spp. for an extended period of transport

This study determined the survivability of methicillin-resistant Staphylococcus aureus (MRSA) and vancomycin-resistant enterococci (VRE) for extended periods of time and temperatures using a standard swab for assessment. Our study showed that transportation in Liquid Amies medium could be performed at room temperature or 4°C for up to 14 days without a decrease in recovery of MRSA or VRE.

Suitability of Commercial Transport Media for Biological Pathogens under Nonideal Conditions

There is extensive data to support the use of commercial transport media as a stabilizer for known clinical samples; however, there is little information to support their use outside of controlled conditions specified by the manufacturer. Furthermore, there is no data to determine the suitability of said media for biological pathogens, specifically those of interest to the US military. This study evaluates commercial off-the-shelf (COTS) transport media based on sample recovery, viability, and quality of nucleic acids and peptides for nonpathogenic strains of Bacillus anthracis, Yersinia pestis, and Venezuelan equine encephalitis virus, in addition to ricin toxin. Samples were stored in COTS, PBST, or no media at various temperatures over an extended test period. The results demonstrate that COTS media, although sufficient for the preservation of nucleic acid and proteinaceous material, are not capable of maintaining an accurate representation of biothreat agents at the time of collection.

Comparison of Copan eSwab with the Copan Venturi Transystem for the quantitative survival of Escherichia coli, Streptococcus agalactiae and Candida albicans

Swab transport systems should preserve the viability and stability of micro-organisms in clinical specimens throughout transport and storage. eSwab, a nylon-tipped swab in liquid medium, designed for better specimen collection and less micro-organism entrapment, was evaluated for the maintenance of viability and quantitative survival of Escherichia coli, Streptococcus agalactiae and Candida albicans. The quantitative elution method was used to evaluate eSwab in vitro. In vitro, the recovery of the three micro-organisms was higher in eSwab (97-100%) as compared to the Copan Venturi Transystem (CVT) (86-96%) at room temperature (RT) for time point 0 h and remained similar after 6 h. E. coli and C. albicans proliferated in both transport systems when preserved beyond 6 h. At 4 degrees C, the recovery of eSwab was higher (>94%) compared to CVT (77-94%) for the micro-organisms tested. eSwab did not only meet the Clinical Laboratory and Standards Institute (CLSI) criteria for microbiological transport devices, but as its recovery rate in vitro was higher than that of CVT, it might also enhance the sensitivity of bacterial culture in the future.

Comparison of the Copan ESwab system with two Amies agar swab transport systems for maintenance of microorganism viability

Swab transport systems are used for a variety of specimen types and must maintain organism viability throughout the transport process. The Copan ESwab is a new nylon-flocked swab designed to optimize specimen collection and to minimize entrapment of the specimen. We used the quantitative elution method with recommended strains, as described in CLSI document M40-A, to evaluate the ESwab for maintenance of viability of aerobic and anaerobic microorganisms for 0, 6, 24, and 48 h during room temperature and refrigerated temperature storage. The Becton Dickinson CultureSwab MaxV swab and the Remel BactiSwab were used as comparators. The ESwab met CLSI acceptance criteria for all aerobic isolates stored at both temperatures and for all anaerobic isolates stored at refrigerated temperature. The ESwab also met CLSI criteria for four of five anaerobic strains at room temperature. Prevotella melaninogenica was not recovered after 24 or 48 h of room temperature storage with any of the three swab transport systems tested. Overall, the ESwab was equivalent to the Becton Dickinson CultureSwab MaxV swab in organism recovery but recovered more isolates than Remel BactiSwab.