Fluorescent Microspheres as Surrogates for <i>Salmonella enterica</i> serotype Typhimurium in Recovery Studies from Stainless Steel

• Main Author: Baker, Rebecca Dain
• Other Authors: Food Science and Technology
• Format: Others
• Published: Virginia Tech 2014
• Subjects: Salmonella Typhimurium; stainless steel; microspheres; bacterial recovery
• Online Access: http://hdl.handle.net/10919/32265; http://scholar.lib.vt.edu/theses/available/etd-05062008-132810/

To compare the optimum recoveries of an inoculation of <i>Salmonella enterica</i> serotype Typhimurium, fluorescent microspheres (1.0 μm diameter, carboxylate-modified, crimson FluoSpheres®, Molecular Probes, Eugene, OR), or a combination of both from stainless steel, three recovery methods, including a standard rinse, a one-ply composite tissue (Kimwipe®) or a sonicating brush were used. Findings were used to assess the effectiveness of fluorescent microspheres as surrogates for <i>S.</i> Typhimurium. For each method, ten coupons (304 grade, 2.5 x 8 cm) were inoculated with either 100 μl of a <i>S.</i> Typhimurium culture, or a solution of fluorescent microspheres, or both, at approximate concentrations of 10⁶. After drying for one hour, coupons were sampled using either a rinse of 100 ml of phosphate buffered saline solution (PBS) for one min, a Kimwipe® tissue method, or submerged in PBS and subjected to a sonicating brush for one min. After treatments, PBS solutions were analyzed using duplicate plate counting (<i>Salmonella</i>) or hemacytometry (microspheres). For microspheres and <i>Salmonella</i>, recovery by sonicating brush > rinse > Kimwipe® method. Additionally, the retention of microspheres on the steel ranged from 16 to 25% (mean from five coupons each recovery method). Microspheres yielded a significantly higher recovery rate (11 â 60%) than <i>Salmonella</i> (~1%) for each recovery method, therefore the microspheres used in this study, are not appropriate surrogates for <i>S.</i> Typhimurium for future recovery studies on stainless steel. However, due to their low standard deviations for their mean percent recovery, they hold the opportunity to provide better accuracy and reproducibility. === Master of Science