A Comparison of Two Flocked swabs: The Copan Elution swab (ESwab™) and the puritan Hydraflock® flocked swab

Background

The use of the most appropriate collection and transport system device is critical for preservation and isolation of clinically significant organisms. Over the past few years, several studies have evaluated the performance of traditional cotton/dacron swabs versus the nylon flocked swab.(2)(3)(4) Things are changing in microbiology labs due to the increased demands for automation. Transport device platforms must now support molecular testing, virology testing and rapid antigen testing, as well as traditional culture methods. As a result, many labs are moving to replace their traditional swabs with superior performing, multi-purpose flocked swabs.

Purpose

In this study, we compared two flocked swab transport systems; the Copan Liquid Amies Elution swab (ESwab™) and the Puritan® Liquid Amies Collection and Transport System (HydraFlock® Swab).

Method

We used the qualitative Roll-Plate method as described in CLSI M40-A(1) to evaluate the two devices listed in Table 2, for viability of clinically significant aerobes. Three ATCC strains listed in Table 1 were inoculated in triplicate from microtiter wells containing 100μl of standardized suspensions onto appropriate agar plates listed in Table 3. Testing was performed at room temperature for the time periods 0, 24 and 48 hrs. Culture plates were read manually and compared to the zero hour colony counts. The difference in counts between the two brands were recorded for the various dilutions and time points.

Results

Organism dilutions which produced countable colonies within the range 30-300 CFU’s were averaged and compared to the zero hour baseline counts. Estimated CFU’s that were greater than 300 were approximated and included for comparison. Both swabs tested met the CLSI criteria for maintenance of the viability of the organisms tested, however, the Copan ESwab™ produced higher counts for all organisms at all time points.

Conclusions

In this study, the Copan ESwab™ demonstrated superior performance evidenced by higher colony counts for all organisms tested. Both swabs maintained organism viability for 48 hours but the higher colony counts demonstrated with the Copan product can have important implications in situations such as surveillance screening (MRSA, GBS etc) when there may be very few organisms present.