Comparison of Optimal Storage Temperature and Collection Reagents for Living Bacterial Cells in Swab Samples

Abstract

Swabs are useful and common sampling tools in various research fields, such as medicine, ecology, biotechnology, forensic medicine, and pollutant monitoring systems. Collection reagents are one of the essential components in sampling. It is important to develop a sample collection kit and designate an appropriate storage temperature because samples need to be stored for a long time. The purpose of this study was to identify the effects of three collection reagents and three storage temperatures on the recovery of living bacteria without media. We selected Escherichia coli and Staphylococcus aureus as representative environmental bacteria. Distilled water (DW), phosphate buffered saline (PBS), and Tris-EDTA (TE) buffer were used as collection reagents and stored at 22°C, 4°C, and −70°C after sampling. The results of using each collection reagent and storage temperature on the bacteria were compared using relative light units (RLU) and the number of colony forming units (CFU). When using −70°C storage temperature and the TE buffer, the number of living bacteria and the RLU values remained constant. It is therefore recommended that the sample be stored at −70°C immediately after collection and a TE buffer solution be used as the collection reagent.

Keywords

• colony forming units
• relative light units
• sampling
• swab
• tris-edta