Introduction Serofast remains a concern of clinicians and syphilis patients. No consensus has been established, however, that defines an effective treatment strategy and clarifies the pathogenesis.

Methods Between August 2011 and July 2015, eligible patients visiting the STD Clinics in ten prefectural-level cities in Jiangsu Province, China, were referred to participate in this study.A total of 517 patients with early syphilis were enrolled and treated in this study.

Results Twelve months after treatment, 79.3% (410/517) of patients achieved serological cure, 20.1% (104/517) were serofast, and 0.6% (3/517) were serological failures. Multivariate analysis demonstrated that older age (>40 years) and lower baseline RPR titer (≤1:8) were associated with serofast status. We also identified 21 T . pallidum molecular subtypes among early syphilis patients and detected a new subtype, 14i/a.Levels of chemerin were higher in the serum of serofast cases than serological cure cases, potentially indicating a novel cytokine marker for serofast in early syphilis patients after therapy.

Conclusion Our data suggested that older age (>40 years) and lower baseline RPR titer (≤1:8) were associated with serofast status in patients with early syphilis. These results indicated that 14i/a type predicted an increasing risk of serofast status,as well as chemerin may be a novel cytokine marker of serofast outcome in early syphilis patients.