title: The Swedish new variant of Chlamydia trachomatis: genome sequence, morphology, cell tropism and phenotypic characterization.
abstract: Chlamydia trachomatis is a major cause of bacterial sexually transmitted infections worldwide. In 2006, a new variant of C. trachomatis (nvCT), carrying a 377 bp deletion within the plasmid, was reported in Sweden. This deletion included the targets used by the commercial diagnostic systems from Roche and Abbott. The nvCT is clonal (serovar/genovar E) and it spread rapidly in Sweden, undiagnosed by these systems. The degree of spread may also indicate an increased biological fitness of nvCT. The aims of this study were to describe the genome of nvCT, to compare the nvCT genome to all available C. trachomatis genome sequences and to investigate the biological properties of nvCT. An early nvCT isolate (Sweden2) was analysed by genome sequencing, growth kinetics, microscopy, cell tropism assay and antimicrobial susceptibility testing. It was compared with relevant C. trachomatis isolates, including a similar serovar E C. trachomatis wild-type strain that circulated in Sweden prior to the initially undetected expansion of nvCT. The nvCT genome does not contain any major genetic polymorphisms - the genes for central metabolism, development cycle and virulence are conserved - or phenotypic characteristics that indicate any altered biological fitness. This is supported by the observations that the nvCT and wild-type C. trachomatis infections are very similar in terms of epidemiological distribution, and that differences in clinical signs are only described, in one study, in women. In conclusion, the nvCT does not appear to have any altered biological fitness. Therefore, the rapid transmission of nvCT in Sweden was due to the strong diagnostic selective advantage and its introduction into a high-frequency transmitting population.
authors.affiliation: National Reference Laboratory for Pathogenic Neisseria, Department of Laboratory Medicine, Clinical Microbiology, örebro University Hospital, örebro, Sweden.
authors.forename: Magnus
authors.initials: M
authors.lastname: Unemo
authors.affiliation: Pathogen Genomics, The Wellcome Trust Sanger Institute, Cambridgeshire, UK.
authors.forename: Helena M B
authors.initials: HMB
authors.lastname: Seth-Smith
authors.affiliation: Molecular Microbiology Group, University Medical School, Southampton General Hospital, Southampton, UK.
authors.forename: Lesley T
authors.initials: LT
authors.lastname: Cutcliffe
authors.affiliation: Molecular Microbiology Group, University Medical School, Southampton General Hospital, Southampton, UK.
authors.forename: Rachel J
authors.initials: RJ
authors.lastname: Skilton
authors.affiliation: Molecular Microbiology Group, University Medical School, Southampton General Hospital, Southampton, UK.
authors.forename: David
authors.initials: D
authors.lastname: Barlow
authors.affiliation: Microbial Pathogenesis Electron Microscope Facility, The Wellcome Trust Sanger Institute, Cambridge, UK.
authors.forename: David
authors.initials: D
authors.lastname: Goulding
authors.affiliation: Department of Clinical Microbiology, Malmö University Hospital, Malmö, Sweden.
authors.forename: Kenneth
authors.initials: K
authors.lastname: Persson
authors.affiliation: Pathogen Genomics, The Wellcome Trust Sanger Institute, Cambridgeshire, UK.
authors.forename: Simon R
authors.initials: SR
authors.lastname: Harris
authors.affiliation: National Reference Laboratory for Pathogenic Neisseria, Department of Laboratory Medicine, Clinical Microbiology, örebro University Hospital, örebro, Sweden.
authors.forename: Anne
authors.initials: A
authors.lastname: Kelly
authors.affiliation: Department of Obstetrics and Gynaecology, Malmö University Hospital, Malmö, Sweden.
authors.forename: Carina
authors.initials: C
authors.lastname: Bjartling
authors.affiliation: National Reference Laboratory for Pathogenic Neisseria, Department of Laboratory Medicine, Clinical Microbiology, örebro University Hospital, örebro, Sweden.
authors.forename: Hans
authors.initials: H
authors.lastname: Fredlund
authors.affiliation: National Reference Laboratory for Pathogenic Neisseria, Department of Laboratory Medicine, Clinical Microbiology, örebro University Hospital, örebro, Sweden.
authors.forename: Per
authors.initials: P
authors.lastname: Olcén
authors.affiliation: Pathogen Genomics, The Wellcome Trust Sanger Institute, Cambridgeshire, UK.
authors.forename: Nicholas R
authors.initials: NR
authors.lastname: Thomson
authors.affiliation: Molecular Microbiology Group, University Medical School, Southampton General Hospital, Southampton, UK.
authors.forename: Ian N
authors.initials: IN
authors.lastname: Clarke
mesh_terms: D001483:Base Sequence; D002690:Chlamydia Infections / Q000175:diagnosis / Q000453:epidemiology / Q000635:transmission; D002692:Chlamydia trachomatis / Q000235:genetics* / Q000254:growth & development / Q000302:isolation & purification / Q000648:ultrastructure; D003951:Diagnostic Errors; D016680:Genome, Bacterial; D006801:Humans; D002479:Inclusion Bodies; D008297:Male; D008969:Molecular Sequence Data; D010641:Phenotype; D010957:Plasmids; D013045:Species Specificity; D013548:Sweden / Q000453:epidemiology; D018523:Tropism