Fig 1.
Diagram of the study.
Fig 2.
Comparison between 3 dry-reagent conditions and the standard reference method, based on an external standard curve.
Serial 10-fold dilution from 1x106 U/ml to 1x100U/ml of M. ulcerans DNA. The serial curve was generated by a linear regression of the threshold cycle (Ct) against the logarithm of M. ulcerans DNA concentration. Each 10-fold dilution was performed in triplicate. One standard deviation to either side of the mean is shown. Standard QPCR Mix refers to the reference method with fresh mix (y = −3.4107x + 40.357); dry-mix condition A refers to the dry mix containing 5% cryo T and 1% cryo P (y = −3.2333x + 39.087); dry-mix condition B refers to the dry mix containing 10% cryo T and 1% cryo P (y = −3.3727x + 39.942); dry-mix condition C refers to the dry mix containing 7.5% cryo T and 0.5% cryo P (y = −3.357x + 39.851). For each assay, the coefficient of correlation was greater than 0.99.
Fig 3.
Comparison of the 3dry-reagents conditions after exposure to a temperature of 50°C for 15 days and the standard reference method, based on an external standard curve.
Serial 10-fold dilutions, from 1x106 U/ml to 1x102 U/ml, of M. ulcerans DNA. The serial curve was generated by linear regression of the threshold cycle (Ct) against the logarithm of M. ulcerans DNA concentration. Each 10-fold dilution was performed in triplicate. One standard deviation on either side of the mean is shown. “Standard QPCR Mix” corresponds to the reference method with fresh mix (y = −3.34x + 39.88); dry mix A is the dry mix containing 5% cryo T and 1% cryo P (y = −3.23x + 43.94); dry mix B is the dry mix containing 10% cryo T and 1% cryo P (y = −3.26x + 38.98); dry mix C is the dry mix containing 7.5% cryo T and 0.5% cryo P (y = −3.19x + 38.55).
Fig 4.
CT values for the 19 weakly positive samples, for 2 conditions.
(A) Ct results for each sample obtained by the fresh mix and the dry mix B, Horizontal bars indicate mean values ± SD. (B) Mean values ± SD and average ΔCt ± SD between fresh mix and dry mix B.
Fig 5.
CT values for the 55 positive samples, for 3 mix conditions.
(A) Ct results for each sample obtained by the fresh mix and the dry mix B in vial or in strip format, Horizontal bars indicate mean values ± SD. (B) Mean values ± SD and average ΔCt ± SD between fresh mix and dry mix B in vial or in strip format.