Molecular characterization of Treponema pallidum subsp. pallidum in Switzerland and France with a new multilocus...

Area of Science:

• Microbiology
• Epidemiology
• Genetics

Background:

• Syphilis, caused by Treponema pallidum subsp. pallidum (TPA), presents a growing public health challenge with increasing incidence.
• Molecular characterization of TPA strains is crucial for understanding its epidemiological re-emergence.

Purpose of the Study:

• To develop and validate a novel, high-resolution multilocus sequence typing (MLST) scheme for TPA.
• To assess the discriminatory power of the new MLST scheme and its utility in epidemiological surveillance.

Main Methods:

• Analysis of 30 TPA genomes to identify suitable typing loci (TP0136, TP0548, TP0705).
• Development of a new MLST scheme incorporating these loci and analysis of 23S rRNA gene mutations for macrolide resistance.
• Testing the scheme on 120 clinical samples from Switzerland and France.

Main Results:

• The new MLST scheme demonstrated high discriminatory power, outperforming previous typing methods.
• Identified 23 distinct allelic profiles among clinical samples.
• Revealed a high prevalence of macrolide resistance (80% of samples) linked to 23S rRNA gene mutations.

Conclusions:

• The proposed MLST scheme provides enhanced resolution for TPA strain typing, aiding in distinguishing TPA from other treponemes and differentiating major clades and subtypes.
• This tool is valuable for epidemiological surveillance of syphilis, tracking strain diversity, and monitoring antimicrobial resistance.