Table 1.
Repetitive sequence regions of sca2 gene investigation.
Fig 1.
Standard curve for Rickettsia typhi qPCR assay.
Assay used plasmid (pGEM-Teasy) carrying ompB or sca2 fragment of R. typhi as target sequences, with concentrations ranging from 1 to 106 copies/μL. The line with the blank triangle represents patient samples.
Fig 2.
Limit of detection of sca2 and ompB qPCR assay.
R. typhi ranging from 0.3 to 3 x 104 PFU of 30 μL of culture media containing R. typhi was spiked into 300 μL of whole blood from two healthy donors. Whole blood without R. typhi was included as the 0-PFU control. R. typhi was detected using different two assays targeting the sca2 (grey) and ompB (black) genes. Each dot represents a Ct value obtained from qPCR for sca2 or ompB. Dashed lines indicate the median with interquartile range (IQR) as error bars. Experiments for each gene were performed in triplicate per donor. The horizontal dashed line at Ct = 40 indicates the positivity cut-off (Ct ≤ 40).
Table 2.
Sensitivity and specificity of sca2 and ompB qPCR assays testing.
Fig 3.
Comparison of Rickettsia target gene copy number using qPCR targeting ompB and sca2.
Bacterial DNA from buffy coat samples (n = 13) were determined using ompB assay (grey) and sca2 assay (black). Grey and black bar represent the median Rickettsia target gene copy numbers with interquartile range (IQR). Difference between assays were compared using Wilcoxon signed-rank test. A p-value <0.05 was considered statistically significant.