FIGURE 7.

Colorimetric RT-LAMP to detect SAR-CoV-2 in RNA extraction–free clinical samples (A) or laboratory-cultured virus (B). Clinical samples were derived from nasopharyngeal swabs placed on guanidine-containing viral transport medium, diluted 1:10. The RT-PCR Ct values for SARS-CoV-2 based on E gene are as follows: CS134 = 31.8, CS135 = 15.3, CS138 = 18.4, CS139 = 21.7, and CS140 = 24.6. RT-LAMP reaction was performed in 20 μL final volume, incubated at 65°C during 30, 40, or 50 min (inactivated virus) using WarmStart^® colorimetric LAMP master mix (NEB #M1800). Both clinical samples and viruses are RNA extraction–free samples. The amplification products (amplicons) were migrated in agarose gel at 2% to confirm amplification, as indicated by the characteristic ladder highlighted by GelRed^® staining. NTC, nontemplate control; CS, clinical sample; and +C, positive control.