Treponema pallidum Detection at Asymptomatic Oral, Anal, and Vaginal Sites in Adults Reporting Sexual Contact with Persons with Syphilis

Detection of Treponema pallidum DNA for diagnosis, resistance identification, and treatment outcome prediction in early syphilis among men who have sex with men

OBJECTIVES

We investigated the use of Treponema pallidum DNA (TP-DNA) for diagnosis, resistance identification, and treatment outcome prediction in early syphilis among men who have sex with men (MSM).

METHODS

MSM seeking care for sexually transmitted infections were prospectively enrolled from September 2021 to August 2024. Oral rinse, rectal swab, and urethral swab samples were tested for TP-DNA. Resistance-associated mutations (RAMs) to macrolides and tetracyclines were identified. Treatment responses were compared between syphilis cases with detected TP-DNA and those without.

RESULTS

Of 656 MSM enrolled, TP-DNA was most frequently detected in oral rinse samples (37.8% [193/510]), followed by rectal swab (20.2% [103/510]) and urethral swab samples (11.6%, 59/510) in clinic visits for early syphilis. TP-DNA was detected in 45.7% (233/510) of early syphilis cases and 0.7% (1/141) of cases without syphilis, resulting in a specificity of 99.3% (95% CI: 96.1-100%) and sensitivity of 45.7% (95% CI: 41.3-50.1%). Secondary syphilis cases had the highest yield of TP-DNA detection (67.6% [117/173]), followed by primary (48.7% [19/39]) and early latent syphilis cases (32.6% [97/298]). The Ct values of T. pallidum PCR in oral rinse samples were significantly lower in cases of higher rapid plasma reagin (RPR) titres (p < 0.001). The rate of T. pallidum harbouring RAMs to macrolides was 58.9% (139/236), increasing over 6-month intervals, from 32.4% (12/37) in 2021 to 77.8% (21/27) in 2023. Cases of detected TP-DNA had greater serological responses to treatments than those without: 80.3% (159/198) vs. 67.0% (156/233) at month 6 (p 0.002) and 84.1% (143/170) vs. 70.3% (137/195) at month 12 (p = 0.002).

DISCUSSION

T. pallidum PCR showed high specificity for the diagnosis of early syphilis, which correlated with RPR titres and treatment response, and lower Ct values in oral rinse samples correlated with higher RPR titres. The high prevalence of T. pallidum strains with RAMs to macrolides argues against using azithromycin to treat syphilis in Taiwan.

Update on syphilis diagnostics

PURPOSE OF REVIEW

Syphilis is rising globally, with resultant increases in morbidity and mortality that disproportionately impact underserved populations. Appropriate screening and testing for syphilis with accurate, reliable, affordable, and timely assays is crucial for combating this epidemic. This review provides a brief overview of laboratory methods for syphilis diagnosis, with a focus on recent updates in diagnostics and directions for future research.

RECENT FINDINGS

Syphilis can be complex and time-consuming to diagnose and stage appropriately. The historic use of darkfield microscopy for diagnosis has been eclipsed by algorithms that include both nontreponemal and treponemal antibody tests for screening and confirmation of active Treponema pallidum infection. Newer diagnostic modalities include nucleic acid amplification assays (NAATs) and point-of-care testing (POCT), which hold promise for increasing identification of active syphilis but have notable limitations. More work is needed to develop accurate, reliable, affordable, and expeditious tests to optimize syphilis diagnosis.

SUMMARY

Algorithms utilizing a combination of serological treponemal and nontreponemal assays remain standard of care for the diagnosis of syphilis, but recently developed NAATs and POCT assays present opportunities to increase syphilis detection. Further research is warranted to improve upon these testing modalities and explore other markers that could aid in syphilis diagnosis.

Novelty in the gut: a review of the gastrointestinal manifestations of syphilis

Syphilis is a systemic infection caused by the spirochete Treponema pallidum. It is transmitted during pregnancy or through sexual contact. Signs and symptoms vary depending on the clinical stage of the disease. Syphilis has been well-studied, and the introduction of penicillin has resulted in a decline in the number of new cases and deaths. Recently, however, there has been a surge in new cases in young people, especially those with human immunodeficiency virus (HIV). This epidemiological shift has been attributed to increased sexual activity, risky sexual behaviors, and immunodeficiency. There is a paucity of data on gastrointestinal (GI) manifestations of syphilis owing to its rarity and lack of physician awareness. T. pallidum can seed to any part of the GI tract, resulting in esophagitis, gastritis, hepatitis, pancreatitis, or proctocolitis. Depending on the affected part of the GI tract, syphilis can present with nausea, vomiting, painless esophageal ulcers, dysphagia, abdominal pain, weight loss due to early satiety, diarrhea, melena, hematochezia, dyschezia, or anorectal ulcers. Given its indolent clinical course and vague presentation, GI syphilis can mimic other GI disorders, which can delay diagnosis and treatment. A detailed medical history, physical examination, serological tests, and endoscopy can provide a definitive diagnosis. Syphilis and its GI complications are usually treated with long-acting intramuscular penicillin benzathine, and rarely with a 14-day course of intravenous penicillin. Herein, we describe the clinical features, etiopathogenesis, diagnosis, and treatment of GI syphilis. This primer should aid clinicians in timely diagnosis and treatment of various presentations of GI syphilis.

Molecular characterization of Treponema pallidum isolates from Brazil

Syphilis remains a public health concern in Brazil, and the data on the characterization and resistance of Treponema pallidum in Brazil is limited. The present study aimed to detect Treponema DNA in the lesions and blood samples obtained from individuals diagnosed with syphilis. The Brazilian isolates were submitted to the Enhanced Centers for Disease Control and Prevention (ECDC) scheme and also analyzed for resistance gene. Treponemal DNA from 18 lesions and 18 blood specimens were submitted for amplification using Polymerase Chain Reaction (PCR) and Polymerase Chain Reaction in Real Time (RT-PCR). Eight samples from lesions and eight from blood were positive in the RT-PCR analysis. Eight lesions and three blood samples were positive using PCR. Two samples exhibited azithromycin resistance. The Brazilian isolate types 14d/g, 14 d/c, 15d/c, and 15d/e were identified using the ECDC scheme. The three subtypes 14d/c, 15d/c, and 15d/e have been identified in Brazil for the first time.

STI pathogens in the oropharynx: update on screening and treatment

PURPOSE OF REVIEW

The rise in antimicrobial resistance in several STI pathogens such as Neisseria gonorrhoeae has become a public health threat as only one first-line treatment remains. Reducing screening interval for gonorrhoea and chlamydia in high-prevalence populations has been proposed to address antimicrobial stewardship, but this remains controversial. This review aimed to revisit the epidemiology of infections at the oropharynx and review the current screening recommendations and treatment guidelines in different populations.

RECENT FINDINGS

Emerging evidence suggests that the oropharynx is the primary anatomical site for gonorrhoea transmission but maybe not for chlamydia transmission. Most international guidelines recommend 3-monthly oropharyngeal gonorrhoea and chlamydia screening for high-prevalence populations (e.g. men who have sex with men) but not low-prevalence populations (e.g. heterosexuals) given the clinical and public health benefits of screening in low-prevalence populations are still unclear. Doxycycline remains the first-line treatment for oropharyngeal chlamydia in most guidelines. However, some countries have moved from dual therapy (ceftriaxone and azithromycin) to monotherapy (ceftriaxone) for oropharyngeal gonorrhoea treatment to address antimicrobial stewardship.

SUMMARY

The transmission of gonorrhoea and chlamydia is still not fully understood. Further work will be required to evaluate the benefits and harms of reducing screening in high-prevalence populations.