Figure 2. Holding time and preservation temperature comparison for log₁₀ bla_KPC (A), bla_OXA-48-like (B), and bla_VIM (C) measured by quantitative PCR in triplicate in study of detection methods for wastewater surveillance of antimicrobial-resistant bacteria from healthcare facilities. Triangles indicate 1 day holding time, circles indicate 7 days, and squares indicate 29 days. Gray symbols indicate 4°C. white symbols indicate –20°C, and black symbols indicate –70°C. All gene copies are normalized to log₁₀ 16S rRNA gene. Horizontal gray lines show the range of values for each treatment. Control sample DNA was extracted immediately upon receipt in laboratory. Raw sample represents processed raw wastewater. Glycerol preserved are unprocessed samples preserved with 50% glycerol with Tris. Concentrated samples were polyethylene glycol precipitated for 2 hours and centrifuged, and the resulting pellet was resuspended and held at the listed temperature.