FIG 3.
Processing of clinical specimens using saponin at different concentrations for selective lysis of human cells. CSF specimens were spiked with S. pneumoniae, H. influenzae, E. coli, HSV2, and adenovirus (A) and NPA specimens spiked with S. pneumoniae, H. influenzae, B. pertussis, and adenovirus (B) were treated with saponin and Triton X-100 to final concentrations indicated in the figure, followed by DNase treatment (see Materials and Methods). Nucleic acids extracted from processed or unprocessed samples were analyzed by real-time PCR assays for β-actin DNA for human DNA and pathogen-specific targets, as described in Table 1. The percentage of DNA was obtained from fold changes calculated from CT values, with respect to CT values for unprocessed samples. The data are the average of data obtained from 3 independent experiments using a total of 4 CSF specimens and 4 NPA specimens. Error bars are the standard error of the mean; statistical significance was calculated by the pairwise Student's t test (two-tailed); *, P < 0.05; **, P < 0.01; ***, P < 0.001.