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Characterization of Chlamydia trachomatis by ompA sequencing and multilocus sequence typing (MLST) in a Swedish county before and after identification of the new variant
  1. Margaretha Jurstrand1,*,
  2. Linus Christerson2,
  3. Markus Klint2,
  4. Hans Fredlund3,
  5. Magnus Unemo3,
  6. Björn Herrmann2
  1. 1 Clinical Research Centre, Örebro University Hospital, SE-70185 Örebro, Sweden;
  2. 2 Department of Clinical Microbiology, University Hospital, SE-751 85 Uppsala, Sweden;
  3. 3 Department of Laboratory Medicine, Section Clinical Microbiology, University Hospital, Örebro, Sweden
  1. Correspondence to: Margaretha Jurstrand, Clinical Research Centre, University hospital, Clinical Research Centre, University hospital, Örebro, SE-701 85, Sweden; margareta.jurstrand{at}orebroll.se

Abstract

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 characterize 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 to ompA sequencing.

Methods: ompA sequencing and MLST was used to characterize 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 to 49.5% utilizing 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.

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