A study by scientists in the United Kingdom provides some new insight into how syphilis—including antibiotic-resistant strains—is spreading in England.
The findings, published late last week in The Lancet Microbe by researchers with the UK Health Security Agency and the Wellcome Trust Sanger Institute, come amid an uptick in syphilis cases in England, which has seen infectious syphilis diagnoses more than triple since 2010. UK health officials believe the rise in syphilis cases reflects both increased testing and transmission, particularly among men who have sex with men (MSM).
In the study, researchers performed whole-genome sequencing (WGS) of samples of Treponema pallidum, the bacterium that causes syphilis, collected from across England from January 2012 through October 2018. Of the 237 genomes that were sequenced, 180 (76%) were from MSM, and about half (118, 49.8%) were from London. Roughly 90% of the genomes contained mutations conferring resistance to macrolide antibiotics.
Discrete clusters associated with sexual behavior
Phylogenomic analysis and clustering revealed two dominant T pallidum sublineages in England: sublineage 1, which was found throughout England and across all patient groups, and sublineage 14, which was found predominantly in MSM ages 34 and older in and around London, with no cases found in the northern regions of England. Further analysis revealed several instances representing discrete heterosexual transmission networks or clusters.
"Our identification of discrete clusters associated with sexual behaviour suggests WGS combined with detailed epidemiological data can resolve some local transmission chains for T pallidum," the study authors wrote. "This could offer opportunities to intervene or educate sexual networks, and to determine or exclude outbreak membership."
Our identification of discrete clusters associated with sexual behaviour suggests WGS combined with detailed epidemiological data can resolve some local transmission chains for T pallidum
The authors say the study demonstrates how genomic surveillance can help with efforts to address the spread of sexually transmitted infections (STIs).
"While its use will need to be investigated further, genomic surveillance could provide a step change in our ability to understand and inform surveillance, prevention, and treatment strategies for a broad range of STIs," senior study author Nicolas Thomson, PhD, said in a press release.