Clinical Report: Prevalent Detection of Treponema pallidum DNA in the Oropharynx

Overview

This retrospective study compared Treponema pallidum PCR positivity in oropharyngeal, anorectal, and urogenital samples from patients with serologically confirmed syphilis. Oropharyngeal samples had the highest positivity rate, including at sites without symptoms or clinical findings. The authors propose prospective evaluation of oropharyngeal sampling as an adjunct to serology in suspected early syphilis when suitable lesion material is unavailable or nondiagnostic.

Background

Syphilis incidence has risen across Europe. Serology remains central to diagnosis, staging, and follow-up, while PCR can directly detect T. pallidum DNA in clinical specimens. The study examined whether detection differed by anatomical site, syphilis stage, and Venereal Disease Research Laboratory (VDRL) titer.

Objective

To compare T. pallidum PCR positivity across three anatomical sampling sites and assess its associations with disease stage and VDRL titer.

Approach

Researchers reviewed records from a specialist sexually transmitted infection clinic in Gdańsk, Poland, for May 2024 through December 2025. The study included 70 adults with serologically confirmed syphilis and 171 anatomical-site samples. The primary adjusted analysis used 168 samples from 69 patients. Not all patients consented to sampling at every site.

Data Highlights

• PCR was positive in 27 of 65 oropharyngeal samples (41.5%), 13 of 65 urogenital samples (20.0%), and 8 of 41 anorectal samples (19.5%).

• Thirty-three of 70 patients (47.1%) had at least one PCR-positive sample.

• Thirty-one of 48 positive samples (64.6%) came from sites with neither local symptoms nor objective clinical findings.

Key Findings

• In the adjusted analysis, oropharyngeal samples had higher odds of PCR positivity than urogenital samples.

• Late or unknown-duration syphilis was associated with lower odds of positivity than early syphilis. Each doubling of VDRL titer was associated with higher odds.

• Analyses of reinfection and concurrent sexually transmitted infections were exploratory; the study did not establish that concurrent infections increased PCR positivity.

Interpretation

The findings show frequent oropharyngeal detection of T. pallidum DNA in this cohort. PCR positivity establishes DNA detection, not organism viability or infectiousness, and does not replace serological testing.

Clinical Implications

Oropharyngeal sampling is a candidate for prospective study as an adjunct to serology when early syphilis is suspected and suitable lesion material is unavailable or lesion-based testing is nondiagnostic. The study does not support routine PCR screening of asymptomatic contacts or unselected high-risk populations.

Limitations

The retrospective, single-clinic study was small, and not all patients underwent three-site sampling. It lacked syphilis-negative oropharyngeal controls and independent molecular confirmation of positive oropharyngeal results, so the assay’s specificity in oral samples could not be directly established.

Conclusion

Oropharyngeal samples had the highest T. pallidum PCR positivity rate in this cohort. Prospective diagnostic studies are needed before oropharyngeal sampling can be recommended for routine practice.

Related Resources & Content

The publication details below appear in the supplied paper or its reference list:

• Kadylak D, Czarny-Kamm J, Pastuszczak M, Sokołowska-Wojdyło M. “Frequent oropharyngeal detection of Treponema pallidum DNA in patients with syphilis: a cross-sectional study of three anatomical sampling sites.” International Journal of Infectious Diseases. 2026;171:109049.

• European Centre for Disease Prevention and Control. “Syphilis.” Annual Epidemiological Report for 2023. European Centre for Disease Prevention and Control. 2025.

• Janier M, Unemo M, Dupin N, Tiplica GS, Potočnik M, Patel R. “2020 European guideline on the management of syphilis.” Journal of the European Academy of Dermatology and Venereology. 2021;35:574–588.

• Papp JR, Park IU, Fakile Y, Pereira L, Pillay A, Bolan GA. “CDC laboratory recommendations for syphilis testing, United States, 2024.” MMWR Recommendations and Reports. 2024;73:1–32.

• Hughes Y, Towns JM, Ong JJ, et al. “The proportion of Treponema pallidum polymerase chain reaction-positive primary syphilis infections that are seronegative for syphilis: a systematic review and meta-analysis.” Open Forum Infectious Diseases. 2025;12:ofaf471.