Relative bacterial release compared to initial uptake (volume-unrestricted setting).

<p>Ratios were determined by comparison of viable counts of absorbed and released bacteria. Results from statistical analysis are shown in <a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0102215#pone.0102215.s003" target="_blank">table S3</a>.</p

Relative bacterial release compared to initial uptake (volume-restricted setting).

<p>Ratios were determined by comparison of viable counts of absorbed and released bacteria. Results from statistical analysis are shown in <a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0102215#pone.0102215.s006" target="_blank">table S6</a>.</p

Some Are More Equal - A Comparative Study on Swab Uptake and Release of Bacterial Suspensions

<div><p>Objectives</p><p>Swabs are widely used to collect samples for microbiological analyses from various clinical settings. They vary by material, size, and structure of the tip. This study investigates the uptake and release capacities for liquid and bacteria.</p><p>Methods</p><p>Five swabs were analyzed for their uptake and release capacities of S<i>taphylococcus aureus</i> and <i>Staphylococcus epidermidis</i> suspensions. Two approaches were investigated providing volume-restricted and unrestricted amounts of bacterial suspensions to mimic various clinical situations. Volume and bacterial uptake and release were measured in milligrams and by counting colony forming units (CFU), respectively.</p><p>Results</p><p>Volume uptake and release in the unrestricted setting varied highly significant between 239.6 mg and 88.7 mg (p<0.001) and between 65.2 mg and 2.2 mg (p<0.001), respectively. In the volume-restricted setting the complete volume was absorbed by all swabs, volume release could only be detected for flocked swabs (2.7 mg; p<0.001). Highest amount of CFU release was detected for the MWE Dryswab in the unrestricted setting for both <i>S. aureus</i> and <i>S. epidermidis</i> with 1544 CFU and 553 CFU, respectively, lowest release for the Sarstedt neutral swab with 32 CFU and 17 CFU, respectively (p<0.001). In the volume-restricted setting MWE Σ-Swab released the highest bacterial amount with 135 CFU <i>S. aureus</i> and 55 CFU <i>S. epidermidis</i>, respectively, the lowest amount was released by Mast Mastaswab with 2 CFU <i>S. aureus</i> and 1 CFU <i>S. epidermidis</i>, respectively (p<0.001). Within the range of the utilized bacterial concentrations, uptake/release ratios were identical for the particular swab types and independent of the bacterial species.</p><p>Conclusions</p><p>The influence of the swab type on subsequent diagnostic results is often underestimated. Uptake and release of the investigated bacteria vary significantly between different swab types and sampling conditions. For best diagnostic outcome swabs should be chosen according to the examined situation and the swab performance profile.</p></div

Release of bacteria in absolute numbers (volume-restricted setting).

<p>Viable counts of bacterial suspension after release by 5 different swab types were determined by serial dilutions and plate counting as described in the methods section. CFU = colony forming units. Results from statistical analysis are shown in <a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0102215#pone.0102215.s005" target="_blank">table S5</a>.</p

Volume uptake and release (volume-unrestricted setting).

<p>Volumes were determined by measuring weight [mg] of round-bottom tubes before and after uptake or deposition of fluids by 5 different swab types. Results from statistical analysis are shown in <a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0102215#pone.0102215.s001" target="_blank">table S1</a>.</p

Release of bacteria in absolute numbers (volume-unrestricted setting).

<p>Viable counts of bacterial suspension after release by 5 different swab types were determined by serial dilutions and plate counting as described in the methods section. CFU = colony forming units. Results from statistical analysis are shown in <a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0102215#pone.0102215.s002" target="_blank">table S2</a>.</p

Relative bacterial release into Amies medium compared to initial uptake (volume-restricted setting).

<p>Ratios were determined by comparison of viable counts of absorbed and released bacteria. Results from statistical analysis are shown in <a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0102215#pone.0102215.s008" target="_blank">table S8</a>.</p

Bacterial release into Amies medium (volume-restricted setting).

<p>Viable counts of bacterial suspension after release by flocked swabs were determined by serial dilutions and plate counting as described in the methods section. CFU = colony forming units. Results from statistical analysis are shown in <a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0102215#pone.0102215.s007" target="_blank">table S7</a>.</p

Volume uptake and release (volume-restricted setting).

<p>Volumes were determined by measuring weight [mg] of round-bottom tubes before and after uptake or deposition of fluids by 5 different swab types. Results from statistical analysis are shown in <a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0102215#pone.0102215.s004" target="_blank">table S4</a>.</p

Qualitative MRSA detection.

<p>Legend: Artificial nose models were inoculated with bacterial suspensions of MRSA and <i>S. epidermidis</i> and defined as 100% MRSA positive. After swabbing with five swab-types (<i>n</i> = 15 swabs per type) MRSA detection rates were analyzed by direct plating or after elution of swab contents into Amies medium. Detection of >1 CFU MRSA on Columbia agar plates supplemented with 5% sheep blood was rated as a positive result. Results of sensitivity analysis are displayed as followed: number of positive results/number of maximal positive results (percentage).</p><p>Qualitative MRSA detection.</p