# Molecular Diagnosis of Syphilis in Brazilian Ambulatory Patients: Detection of Treponema pallidum subsp. pallidum in Serum Using Ancient DNA Protocols

## TL;DR

This study shows that ancient DNA methods can improve syphilis detection in blood samples, offering a better alternative to traditional tests.

## Contribution

The study introduces the use of ancient DNA protocols for molecular diagnosis of syphilis in serum samples.

## Key findings

- aDNA protocols successfully amplified T. pallidum DNA in 82.35% of serum samples.
- T. pallidum sequences were confirmed in 70.59% of the tested samples.
- Molecular approaches using aDNA methods show potential for improving syphilis detection and surveillance.

## Abstract

The rising incidence of syphilis in recent decades underscores the need to improve diagnostic and control strategies. The infection caused by Treponema pallidum subsp. pallidum is commonly diagnosed using serological tests. However, these methods exhibit limitations in the early or late stages of disease, when antibody responses and/or bacterial loads are low. Molecular biology detection using serum samples is also hampered by low circulating bacterial loads during asymptomatic periods. Ancient DNA (aDNA) studies apply methods adapted to recovering low concentrations and degraded DNA. In this study, we evaluated the effectiveness of aDNA protocols applied to the molecular diagnosis of T. p. subsp. pallidum in serum samples from ambulatory patients from Rio de Janeiro, Brazil. A PRISMA-based systematic review was also performed to identify studies using molecular biology diagnosis from serum. Twenty serums screened by TPHA (Treponema pallidum Hemagglutination assay) and with different VDRL titers (Venereal Disease Research Laboratory test) were analyzed. Amplification of tpp15 gene was observed in 14/17 (82.35%) samples; T. pallidum sequence was confirmed in 12/17 (70.59%). The findings demonstrate the potential of molecular approaches based on aDNA-adapted protocols as alternatives to conventional serological diagnosis, contributing to improved detection of infection and strengthening epidemiological surveillance of syphilis.