Molecular Epidemiology of Chlamydia trachomatis Infections

Chlamydia trachomatis is the world’s most prevalent bacterial sexually transmitted pathogen, responsible for urethritis, cervicitis, pelvic inflammatory disease, ectopic pregnancy and infertility, as well as ocular disease in endemic regions. Molecular epidemiology combines pathogen genomics with population-level surveillance to map strain diversity, transmission networks and risk factors. Early approaches relied on sequencing the ompA gene, encoding the major outer-membrane protein, to define serovars linked to distinct clinical syndromes: serovars A–C for trachoma, D–K for urogenital infection and L1–L3 for lymphogranuloma venereum. Advances in typing—multilocus sequence typing (MLST), multilocus variable-number tandem-repeat analysis (MLVA) and core genome phylogenies—have greatly increased discriminatory power, revealing micro-epidemics, bridging infections between sexual networks and the impact of recombination on pathogen evolution. Whole-genome sequencing has begun to characterise antibiotic susceptibility determinants and emerging variants. Insights from global and local studies inform targeted screening, outbreak response and vaccine design by identifying dominant strains in key populations and regions. Integrating molecular data with demographic and behavioural information underpins precision public health strategies to curb the burden of C. trachomatis infection.

Research from Nature Portfolio

Recent studies have refined our understanding of serovar distribution in Europe by sequencing the omp1 gene from diverse clinical specimens collected between 2014 and 2017. Analyses revealed that serovar E accounts for over half of urogenital and ocular infections, with serovars F, D/Da and G/Ga comprising most remaining cases. Follow-up sampling demonstrated stable serovar patterns within patients, underscoring limited intra-host variation. These data clarify the link between serovar prevalence and clinical presentation, highlighting serovar E as a prime target for future vaccine antigens and guiding surveillance programmes in settings with mixed ocular and genital disease.

Molecular Epidemiology of Chlamydia trachomatis Infections publication trend

The graph below shows the total number of articles in molecular epidemiology of chlamydia trachomatis infections across all publications each year (not limited to Nature Index journals).

Technical terms

ompA gene: Gene encoding the major outer-membrane protein, central to serovar classification of C. trachomatis.

Serovar: Subdivision of a bacterial species based on antigenic differences in surface proteins, often linked to clinical manifestations.

Multilocus sequence typing (MLST): Genotyping method using sequences from multiple housekeeping genes to assign isolates to sequence types.

Multilocus variable-number tandem-repeat analysis (MLVA): Typing technique based on variation in the number of tandem repeat units at multiple genomic loci.

Core genome: Set of genes shared by all strains of a species, used to infer high-resolution phylogenetic relationships.

Lymphogranuloma venereum (LGV): Invasive C. trachomatis infection caused by serovars L1–L3, associated with proctitis and systemic dissemination.

Recombination: Genetic exchange between strains or serovars that generates novel variants and influences epidemiological patterns.

References

1. Chlamydia trachomatis serovars in urogenital and ocular samples collected 2014–2017 from Austrian patients. Scientific Reports (2019).
2. Genetic Characterization of Non-Lymphogranuloma venereum Chlamydia trachomatis Indicates Distinct Infection Transmission Networks in Spain. International Journal of Molecular Sciences (2023).
3. Ensuring equity with pre-clinical planning for chlamydia vaccines. npj Vaccines (2023).
4. Unveiling the Multilocus Sequence Typing (MLST) Schemes and Core Genome Phylogenies for Genotyping Chlamydia trachomatis. Frontiers in Microbiology (2018).