Current routine diagnostic methods for the detection of Chlamydia trachomatis (CT) do not provide information on CT viability. Previously, detection of messenger-RNA (mRNA) has been utilized as a marker for bacterial viability, as mRNA molecules are generally short-lived (half-life of minutes). However, only one study evaluated CT mRNA halflife times [t 1/2 ] of two clinical isolates (serovar L2b and E) which ranged from 1 to !5000 minutes. Here we assess and confirm mRNA half-life times of

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... var D to further facilitate evaluation of CT viability. Methods CT serovar D was propagated in HeLa cells until 30 h post infection and treated with rifampicin to arrest gene transcription. Total RNA was isolated at 0 min (before treatment), and 10 min, 30 min and 60 min after treatment. RNA was converted to cDNA using random hexamers. RT-qPCR was used to amplify fragments of the unprocessed 16S (intermediate molecules in 16S rRNA synthesis), 16S (early), rpoD (early), omcB (mid), and hctA (late) gene transcripts. Half-life time was based on the fit of an exponential decay between values obtained at before and after transcriptional arrest. Results In this study showed that the obtained t 1/2 values for CT serovar D mRNA (median t 1/2 18 min) were similar as previously reported for the CT serovars L2b and E (median t 1/2 15 and 17 min, respectively). The observed half-lifes of rpoD (9 min), hctA (12 min), omcB (18 min), and unprocessed 16S (18 min) transcripts were relatively short, while 16S gene transcripts were more stable over time (t 1/2 54 min). Conclusion The detection of rpoD, hctA, omcB, and unprocessed 16S gene transcripts showed the most promising results as a potential marker for an active CT infection. Currently we are evaluating the time to clearance of mRNA molecules in patients after being treated. Disclosure No significant relationships.