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Epidemiology
Original article
Ten years transmission of the new variant of Chlamydia trachomatis in Sweden: prevalence of infections and associated complications
  1. Jenny Dahlberg1,
  2. Ronza Hadad2,
  3. Karin Elfving3,
  4. Inger Larsson4,
  5. Jenny Isaksson1,
  6. Anders Magnuson5,
  7. Hans Fredlund2,
  8. Magnus Unemo2,
  9. Bjőrn Herrmann1
  1. 1 Section of Clinical Bacteriology, Department of Medical Sciences, Uppsala University, Uppsala, Sweden
  2. 2 WHO Collaborating Centre for Gonorrhoea and other STIs, Örebro University, Örebro, Sweden
  3. 3 Department of Clinical Microbiology, Falu Lasarett, Falun, Sweden
  4. 4 Department of Clinical Microbiology, Sunderby Hospital, Luleå, Sweden
  5. 5 Department of Clinical Epidemiology and Biostatistics, School of Medical Sciences, Örebro University, Örebro, Sweden
  1. Correspondence to Dr Bjőrn Herrmann, Section of Clinical Bacteriology, Department of Medical Sciences, Uppsala University, SE-75185 Uppsala, Sweden; bjorn.herrmann{at}medsci.uu.se

Abstract

Objectives In 2006, a new variant of Chlamydia trachomatis (nvCT) was discovered in Sweden. It has a deletion in the plasmid resulting in failed detection by the single target systems from Abbott and Roche used at that time, whereas the third system used, from Becton Dickinson (BD), detects nvCT. The proportion of nvCT was initially up to 65% in counties using Abbott/Roche systems. This study analysed the proportion of nvCT from 2007 to 2015 in four selected counties and its impact on chlamydia-associated complications.

Methods C. trachomatis-positive specimens collected from 2007 to 2015 were analysed by a specific PCR to identify nvCT cases. Genotyping was performed by multilocus sequence typing (MLST) and ompA sequencing. Ectopic pregnancy and pelvic inflammatory disease records were extracted from the national registers.

Results In total, 5101 C. trachomatis-positive samples were analysed. The nvCT proportion significantly decreased in the two counties using Roche systems, from 56% in 2007 to 6.5% in 2015 (p<0.001). In the two counties using BD systems, a decrease was also seen, from 19% in 2007 to 5.2% in 2015 (p<0.001). Fifteen nvCT cases from 2015 and 102 cases from 2006 to 2009 had identical MLST profiles. Counties using Roche/Abbott systems showed higher mean rates of ectopic pregnancy and pelvic inflammatory disease compared with counties using BD systems.

Conclusions The nvCT proportion has decreased in all counties and converged to a low prevalence irrespective of previous rates. Genotyping showed that nvCT is clonal and genetically stable. Failing detection only marginally affected complication rates.

  • chlamydia trachomatis
  • epidemiology
  • plasmid
  • pelvic inflammatory disease
  • ectopic pregnancy

This is an Open Access article distributed in accordance with the Creative Commons Attribution Non Commercial (CC BY-NC 4.0) license, which permits others to distribute, remix, adapt, build upon this work non-commercially, and license their derivative works on different terms, provided the original work is properly cited and the use is non-commercial. See: http://creativecommons.org/licenses/by-nc/4.0/

https://doi.org/10.1136/sextrans-2016-052992

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    Footnotes

    • Handling editor Jackie A Cassell

    • Contributors BH, HF and MU designed the study; BH, KE, IL, HF and MU coordinated the study and all surveillance sites; JD, JI and RH performed all the laboratory work; JD, RH and BH performed the initial data analysis; AM performed statistical analysis; JD and BH, with support of RH, HF and MU, wrote the first draft of manuscript. All authors contributed to the finalisation of the manuscript.

    • Funding This work was supported by grants from local funds at Uppsala University Hospital and from the Örebro County Council Research Committee and the Foundation for Medical Research at Örebro University Hospital, Sweden.

    • Competing interests None declared.

    • Ethics approval The study was approved by the Regional Ethical Review Board in Uppsala, Sweden (Dnr2007/312).

    • Provenance and peer review Not commissioned; externally peer reviewed.