Impact of culture-enrichment on qPCR detection of <i>Streptococcus pneumoniae</i> gene <i>lytA</i> in saliva from schoolchildren.

<p>Each dot or cross represents an individual sample. The position of symbols corresponds to C<i>_T</i> values for <i>lytA</i>-specific signals in DNA extracted from raw and culture-enriched sample of saliva as marked on corresponding axes. Dots represent 44 samples classified as positive and crosses represent 6 samples classified as negative for <i>S. pneumoniae</i> with qPCR. Open dots represent 32 saliva samples classified as positive <i>for S. pneumoniae</i> in both raw and culture-enriched samples. Green dots represent 12 samples classified as positive only after culture-enrichment. Dotted lines mark the threshold assigned to discriminate between positive (C<i>_T</i> <40) and negative samples, and the total number of 45 cycles in each qPCR reaction. There was a significant increase in quantity of both <i>lytA</i> and (not shown) <i>piaA</i> detected with qPCR in culture-enriched compared to raw saliva samples (Mann-Whitney, p = <0.0001).