Poster Presentation 15th Lorne Infection and Immunity 2025

Rapid point of care self-test for diagnosis of active syphilis  (#325)

Shuning Zheng 1 , Elsie Williams 1 , Lilian Hor 1 , Helen Wei 1 , Sarah Hess 1 , Felicia Schlotthauer 1 , Rob Center 1 2 , Minh Pham 1 , Ewa Michalak 1 3 , Peter Newman 1 , Michael Traeger 1 , David Wang 1 , Rohit Ketkar 4 , Ibrahim Tabbouche 4 , Curtis Hung 4 , Diana Piccoli 1 , Thomas Mikeska 1 5 , Ying Zhang 6 7 , Reuben Kiggundu 6 7 , Mark Stoove 1 7 8 , Jason Ong 6 7 , Heidi E Drummer 1 2 9
  1. Burnet Institute, Melbourne, VIC, Australia
  2. Department of Microbiology and Immunology, University of Melbourne, Melbourne, VIC, Australia
  3. Present address, Walter and Eliza Hall Institute, Parkville, VIC, Australia
  4. Atomo Diagnostics, Leichhardt, NSW, Australia
  5. Present address, Crux BioLabs, Bayswater, VIC, Australia
  6. Melbourne Sexual Health Centre, Melbourne, VIC, Australia
  7. Monash University, Clayton, VIC, Australia
  8. Deakin University, Geelong, VIC, Australia
  9. Department of Microbiology, Monash University, Melbourne, VIC, Australia

Background:

Syphilis, caused by Treponema pallidum (TP), is a sexually transmitted infection. Cases of syphilis have increased three-fold in Australia over the past 10 years, now numbering ~6000 per year. Globally, WHO estimates that 8 million adults acquired syphilis in 2022, with outcomes including 200,000-300,000 neonatal deaths and still births. While treatment is straightforward and cost-effective using long-acting penicillin, diagnosis typically requires multiple patient interactions with trained health care practitioners and testing in centralised laboratories. Furthermore, traditional tests for anti-treponemal antibodies cannot distinguish active versus past-treated infections. There remains an urgent need to develop simple, quick, point-of-care tests to diagnose active syphilis to reduce the burden of disease.

Methods:

Clinical samples collected from the Melbourne Sexual Health Centre (625/22) were used to develop a lateral flow assay and select the best performing Treponema pallidum antigen combination for discriminating active and past-treated syphilis. Samples included 40 confirmed patient cases of active syphilis, 41 past-treated and 17 volunteers with no history of syphilis infection. Performance of the Burnet Active Syphilis test prototype was assessed against two commercial tests, Abbott BioLine 3.0 ™ and Abbott Determine™ Syphilis TP and developed using the AtomoRapidTM Pascal self-testing device.

 Results:

We have developed a 15-minute one-step TP lateral flow assay (BDI Active Syphilis). The test has an integrated lancet, buffer delivery system and integrated blood collection unit that delivers 10ul blood. The final prototype provides 95% sensitivity for active syphilis, 100% specificity for never infected and 86% (no exclusion criteria) to 93% (with exclusion criteria applied) combined specificity for past-treated and never infected, which outperforms the existing commercial tests. HIV status did not impact performance. The BDI Active Syphilis test provides a simple one-step test to accurately identify patients with current infection and is amenable to self-testing at home or health care practitioner supervised testing.