New insights into Chlamydia trachomatis LGV diversity may help curb STI spread

New insights into Chlamydia trachomatis LGV diversity may help curb STI spread | Image Credit: © Khunatorn - © Khunatorn - stock.adobe.com.

Diversity within the ompA-genotype L2b clade has been highlighted, increasing understanding of pathogens linked to sexually transmitted infections (STIs) that may reduce their spread, according to a recent study published in Microbial Genomics.¹

There are hundreds of millions of new STI cases reported worldwide per year, according to the World Health Organization.² Symptoms are often silent, leading to increased transmission, disease, and complications.

Many pathogens are grown in laboratories, with significant amounts of human DNA in clinical samples, creating research barriers. In Chlamydia trachomatis, lymphogranuloma venereum (LGV) has been reported as an invasive biovar.¹

“Comprehensive nationwide prevalence data for C. trachomatis are lacking in Argentina, as is the identification of all LGV cases; however, the limited data suggest higher rates of LGV in Buenos Aires than in Europe,” wrote investigators.¹

The study was conducted to investigate LGV genomes in Argentina and Finland, broadening analysis of LGV genomes. Participants included adult patients with proctitis-compatible symptoms and STI risk factors from September 2017 to August 2023. Rectal swab samples were collected from these patients.¹

SureSelect XT HS2 DNA was used to perform target enrichment of clinical samples. Baits were designed to cover all C. trachomatis diversity. Genomes with over 95% covered were considered acceptably complete.¹

There were 32 C. trachomatis LGV genomes included in the final analysis, 21 of which fell within the ompA-genotype L2b clade. Two genomically identical samples from 2 separate locations were reported in a single patient, highlighting locally circulating strains within the community.¹

Two Argentinian samples form 2017 and 2023 presented with identical genomes to many European samples. This indicated a less clock-like mutation from C. trachomatis compared to other species. Strong circulation of C. trachomatis LGV lineage was also noted.¹

Investigators also reported a new lineage defined by a branch of over 200 single nucleotide polymorphisms. Two samples were taken in April 2018 and August 2018 in 1 patient, indicating reinfection with a different strain following treatment.¹

The most similar to the ompA gene of the L4 clade was of ompA-genotype L1. However, 10 nucleotide substitutions were identified.¹

“Taking into account this level of diversity from all previously described LGV genomes and the number of samples defining the clade (n=11), we propose the new ompA-genotype L4,” wrote investigators.¹

Comparisons of patients in clades L2b and L4 were also performed. An anorectal inflammatory tumour was reported in 50% of patients with LGV from the ompA-genotype L4 clade vs 25% with the ompA-genotype L2b clade. Other concomitant STIs were reported in 50% and 30%, respectively.¹

One sample fell within the Urogenital T1 lineage. The recombination events defining this branch cover the same loci often affected by the recombination in the T1 lineage strains.¹

This data highlights widespread distribution of ompA-genotype L2b. Investigators noted this genomic clause as a primary source of LGV, with recent evolved diversity in the clade.¹

“It confirms that in locations distant from the most studied European part of the outbreak such as Argentina, strains identified as L2 by ompA-genotyping also present the genetic backbone of ompA-genotype L2b,” wrote investigators. “Our data suggest that in Buenos Aires, there have been multiple introduction events of this ompA-genotype L2b clade.¹

References

1. Büttner KA, Wegner F, Bregy V, et al. Chlamydia trachomatis genomes from rectal samples: description of a new clade comprising ompA-genotype L4 from Argentina. Microbial Genomics. 2025;11(2). doi:10.1099/mgen.0.001350
2. Curbing the global spread of sexually transmitted diseases. EurekAlert. February 13, 2025. Accessed February 24, 2025. https://www.eurekalert.org/news-releases/1073641