Chlamydia trachomatis is the world's most prevalent bacterial sexually transmitted infection and leading infectious cause of blindness, yet it is one of the least understood human pathogens, in part due to the difficulties of in vitro culturing and the lack of available tools for genetic manipulation. Genome sequencing has reinvigorated this field, shedding light on the contemporary history of this pathogen. Here, we analyze 563 full genomes, 455 of which are novel, to show that the history of the species comprises two phases, and conclude that the currently circulating lineages are the result of evolution in different genomic ecotypes. Temporal analysis indicates these lineages have recently expanded in the space of thousands of years, rather than the millions of years as previously thought, a finding that dramatically changes our understanding of this pathogen's history. Finally, at a time when almost every pathogen is becoming increasingly resistant to antimicrobials, we show that there is no evidence of circulating genomic resistance in C. trachomatis.

We describe detection in the United Kingdom (UK) of the drug-resistant Neisseria gonorrhoeae FC428 clone, with ceftriaxone resistance and intermediate azithromycin resistance. Two female patients developed infection following contact with UK-resident men from the same sexual network linked to travel to Ibiza, Spain. One case failed treatment with ceftriaxone, and azithromycin and gentamicin, before successful treatment with ertapenem. Both isolates had indistinguishable whole-genome sequences. Urgent action is essential to contain this drug-resistant strain.

The use of whole-genome sequencing as a tool for the study of infectious bacteria is of growing clinical interest. Chlamydia trachomatis is responsible for sexually transmitted infections and the blinding disease trachoma, which affect hundreds of millions of people worldwide. Recombination is widespread within the genome of C. trachomatis, thus whole-genome sequencing is necessary to understand the evolution, diversity, and epidemiology of this pathogen. Culture of C. trachomatis has, until now, been a prerequisite to obtain DNA for whole-genome sequencing; however, as C. trachomatis is an obligate intracellular pathogen, this procedure is technically demanding and time consuming. Discarded clinical samples represent a large resource for sequencing the genomes of pathogens, yet clinical swabs frequently contain very low levels of C. trachomatis DNA and large amounts of contaminating microbial and human DNA. To determine whether it is possible to obtain whole-genome sequences from bacteria without the need for culture, we have devised an approach that combines immunomagnetic separation (IMS) for targeted bacterial enrichment with multiple displacement amplification (MDA) for whole-genome amplification. Using IMS-MDA in conjunction with high-throughput multiplexed Illumina sequencing, we have produced the first whole bacterial genome sequences direct from clinical samples. We also show that this method can be used to generate genome data from nonviable archived samples. This method will prove a useful tool in answering questions relating to the biology of many difficult-to-culture or fastidious bacteria of clinical concern.

Syphilis, which is caused by the sexually transmitted bacterium Treponema pallidum subsp. pallidum, has an estimated 6.3 million cases worldwide per annum. In the past ten years, the incidence of syphilis has increased by more than 150% in some high-income countries, but the evolution and epidemiology of the epidemic are poorly understood. To characterize the global population structure of T. pallidum, we assembled a geographically and temporally diverse collection of 726 genomes from 626 clinical and 100 laboratory samples collected in 23 countries. We applied phylogenetic analyses and clustering, and found that the global syphilis population comprises just two deeply branching lineages, Nichols and SS14. Both lineages are currently circulating in 12 of the 23 countries sampled. We subdivided T. p.pallidum into 17 distinct sublineages to provide further phylodynamic resolution. Importantly, two Nichols sublineages have expanded clonally across 9 countries contemporaneously with SS14. Moreover, pairwise genome analyses revealed examples of isolates collected within the last 20 years from 14 different countries that had genetically identical core genomes, which might indicate frequent exchange through international transmission. It is striking that most samples collected before 1983 are phylogenetically distinct from more recently isolated sublineages. Using Bayesian temporal analysis, we detected a population bottleneck occurring during the late 1990s, followed by rapid population expansion in the 2000s that was driven by the dominant T. pallidum sublineages circulating today. This expansion may be linked to changing epidemiology, immune evasion or fitness under antimicrobial selection pressure, since many of the contemporary syphilis lineages we have characterized are resistant to macrolides.

ObjectivesUnderstanding the public health impact of lymphogranuloma venereum (LGV) in Europe is hampered by inadequate diagnostics and surveillance systems in many European countries. We developed and piloted LGV surveillance in three European countries without existing systems and performed a preliminary investigation of LGV epidemiology, where little evidence currently exists.MethodsWe recruited STI or dermatovenereology clinics and associated laboratories serving men who have sex with men (MSM) in Austria, Croatia and Slovenia, using the UK for comparison. We undertook centralised LGV testing of Chlamydia trachomatis (CT)-positive rectal swabs collected between October 2016 and May 2017 from MSM attending these clinics. Stored specimens from Austria (2015–2016) and Croatia (2014) were also tested. Clinical and sociodemographic data were collected using a standardised proforma. The ompA gene of LGV-positive specimens was sequenced.ResultsIn total, 500 specimens from CT-positive MSM were tested, and LGV positivity was 25.6% (128/500; 95% CI 22.0% to 29.6%) overall, and 47.6% (79/166; 40.1% to 55.2%) in Austria, 20.0% (3/15; 7.1% to 45.2%) in Croatia, 16.7% (1/6; 3.0% to 56.4%) in Slovenia and 14.4% (45/313; 10.9% to 18.7 %) in the UK. Proformas were completed for cases in Croatia, Slovenia and in the UK; proformas could not be completed for Austrian cases, but limited data were available from line listings. Where recorded, 83.9% (78/93) of LGV-CT cases were HIV-positive compared with 65.4% (149/228) of non-LGV-CT cases; MSM with LGV-CT were more likely to have proctitis (Austria, 91.8% vs 40.5%, p<0.001; Croatia, 100% vs 25%, p=0.04; UK, 52.4% vs 11.7%, p<0.001) than those with non-LGV-CT. Six different ompA sequences were identified, including three new variants; the L2 ompA sequence predominated (58.6%, 51/87).ConclusionsLGV is substantially underdiagnosed in MSM across Europe. Unified efforts are needed to overcome barriers to testing, establish effective surveillance, and optimise diagnosis, treatment and prevention.