Evaluation of bacterial recovery and viability from three different swab transport systems

This study evaluated three types of swab transport systems for organism recovery. Swabs with transport media were further assessed for organism viability over 24 hours over a range of different storage temperatures. Test organisms consisted of aerobes, fastidious aerobes and anaerobes. Swabs were tested according to the standardised quantitative elution method published by the Clinical Laboratory Standards Institute (CLSI; M-40A). There were substantial differences in primary organism recovery with recovery rates from different swabs ranging from <0.1% to 78% for Streptococcus pyogenes. Similar differences were noted for other test organisms. In general, the flocked swab (ESwab) demonstrated highest rates of recovery for aerobic organisms, while higher rates of recovery of Fusobacterium nucleatum were demonstrated from a standard swab (Transwab). When considering organism viability, no single swab fulfilled all the criteria stipulated by the M-40A standard for all organism/temperature combinations. Organism viability was marginally better for the gel-based swab transport systems as compared to the liquid-media based ESwab. Significant differences between swab transport systems were demonstrated, including differences for primary organism recovery and viability. The ESwab showed the best recovery of organisms, while gel-based media demonstrated marginally better bacterial viability for most tested retention times and temperatures.