Introduction Performing a test of cure (TOC) could demonstrate success or failure of antimicrobial treatment of C. trachomatis (CT) infection, but the value of using a nuclear acid amplification test (NAAT) based TOC after treatment is subject to discussion, as the presence of CT nucleic acids after treatment may be prolonged and intermittent without the presence of infectious bacteria. We used cell culture to assess if a NAAT positive TOC indicates the presence of viable CT.

Methods We analysed follow up (FU) data from women with a CT infection who visited the STI clinic of Amsterdam, the Netherlands, from September 2015 through June 2016. After giving informed consent, participants underwent baseline and three FU speculum examinations to obtain cervical swabs for both CT culture and NAAT testing. Speculum examinations were scheduled at 7, 21 and 49 days after treatment (single dose 1000 mg azithromycin). Collected samples were analysed using a RNA and DNA-based NAAT. CT cell culture was performed on all samples at baseline, and in FU samples that were NAAT-positive. Clearance was defined as conversion to negative NAAT results at any FU visit.

Results We included 78 women with NAAT proven CT infection prior to receiving treatment of whom 58 (74%) were also culture positive. At the first visit after treatment (median 7 days; IQR 7–8) 44 (47%) women were NAAT positive, of whom three tested also positive by culture. CT infection was cleared in 73 women (94%), of whom 61 (78%) at their second FU visit (median 21 days; IQR 21–25). Of the five women who did not clear their infection, three were also culture positive indicating a viable infection. All five reported unprotected sexual contact after inclusion prior to their last FU visit, indicating potentially new infections.

Conclusion We observed prolonged and intermittent positive results over time for both NAAT tests. For three participants (4%) viable CT infections were detected 49 days after treatment. All three cases reported new sexual contacts. In conclusion, persisting infections or treatment failure were rare.

Support: Hologic provided Aptima test materials and kits in-kind. Roche provided Cobas test materials and kits in- kind. Copan provided Universal Transport Medium in-kind