Objectives: A new variant C. trachomatis (nvCT) strain has been recently isolated in Sweden, which has a 377bp deletion in a portion of the plasmid that is the target area for some C. trachomatis nucleic acid amplification tests (NAAT). Consequently these platforms generate false negative results when presented with this strain. This study aimed to determine if nvCT was present within England and Wales.
Methods: Specimens, which had been determined to be C. trachomatis positive using an unaffected platform (Strand Displacement Assay, Aptima Combo 2 and RealArt) were tested for the presence of the deletion using an in-house nested PCR assay which generated a 253bp fragment in new variant strains and a 630bp fragment in wild-type strains. The specimens tested could be divided into two main groups: (i) 933 specimens sourced from patients attending both Genito Urinary medicine services and the National Chlamydia Screening programme were forwarded from eight key laboratories within England and Wales. (ii) 179 specimens were sourced from men who have sex with men patients and forwarded from 30 clinics throughout the UK.
Results: A total of 1112 specimens were screened for the presence of the 377bp deletion. A total of 1066 were identified by an in-house PCR method to be wild type strains. Forty-six strains failed to generate an amplicon and were therefore untypable. This is consistent with differences in the analytical sensitivity of different NAATs and probably reflective of low C. trachomatis DNA load. No nvCT strains were identified.
Conclusion: Currently there is no evidence that nvCT is present within England and Wales. However screening and prevalence studies are ongoing and UK clinicians and microbiologist should remain vigilant for suspicious, negative results.
- 377bp deletion
- new variant
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