Objectives In 2006 a new variant of Chlamydia trachomatis (nvCT), with a deletion in the cryptic plasmid, was reported in Sweden. This deletion included the targets for the genetic diagnostic systems used in many clinical laboratories and resulted in thousands of false-negative results. The aim of this study was to characterise consecutive Chlamydia tissue culture-positive samples from 2006 in Örebro County, after identification of the nvCT, and to compare the results from samples collected in the same county in 1999–2000. The study also aimed to evaluate the discriminatory capacity of multilocus sequence typing (MLST) compared with ompA sequencing.
Methods ompA sequencing and MLST was used to characterise 100 consecutive Chlamydia tissue culture-positive samples.
Results A significant (p<0.001) increase of genotype E, from 47% in 1999–2000 to 69% in 2006, was detected. All 41 nvCT isolates from 2006 displayed an identical ompA genotype E and MLST profile. Excluding the nvCT isolates, the distribution of ompA genotypes is similar to the genotyping results from 1999–2000. Among the wild-type genotype E isolates from 2006, 14 unique MLST sequence types were obtained from 26 isolates while they were identical in ompA genotyping. The discriminatory power (D) of C trachomatis strains in this material was 83.5% using the MLST system compared with 49.5% utilising ompA sequencing.
Conclusion In all, MLST enables improved studies of the molecular epidemiology of C trachomatis. All nvCT isolates from 2006 displayed an identical ompA genotype E and MLST profile, which strongly indicates a clonal spread of the nvCT.
- Chlamydia trachomatis
- laboratory diagnosis
- molecular typing
- multilocus sequence typing
- multilocus sequence typing
- nucleic acid amplification test
- new variant of Chlamydia trachomatis
- outer membrane protein A
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The work of this manuscript is part of the goals described in the European Framework Programme 6 (FP6) funded EpiGenChlamydia Consortium (EU FP6 LSHG-CT-2007-037637) a co-ordination actions in functional genomics research entitled: ‘Contribution of molecular epidemiology and host–pathogen genomics to understand Chlamydia trachomatis disease’ (see additional information at http://www.EpiGenChlamydia.EU).
Funding This work was supported by grants from the Örebro Medical Research Foundation, Örebro University Hospital, the Uppsala-Örebro Regional Research Council, the National Board of Health and Welfare, Stockholm, and the National Institute for Public Health, Östersund, Sweden.
Competing interests None.
Provenance and peer review Not commissioned; externally peer reviewed.