Risk Factors for Syphilis in MSM According to HIV Status

Treponema pallidum, syphilis
Treponema pallidum, syphilis
Among men who have sex with men, those with HIV were found to engage more often in sexual behaviors associated with syphilis than those without HIV.

Among men who have sex with men (MSM), those with HIV were found to engage more often in sexual behaviors associated with syphilis than those without HIV, according to study results published in BMC Infectious Diseases.

This prospective study was conducted with data from 2015 from a sexually transmitted infections unit in Barcelona, Spain. Patients completed a self-administered questionnaire that included demographic and sexual behavior information from the previous 12 months. Initial screening for syphilis consisted of a specific test for antibodies against Treponema pallidum; any subsequent positive results were confirmed by a non-treponemal test and another treponemal test. All syphilis cases were confirmed by positive dark-field microscopy or polymerase chain reaction positive for T pallidum.

Overall, there were 270 patients:274 cases classified as having early syphilis, 76 cases of primary syphilis, 140 of secondary syphilis, and 58 of early latent syphilis. The majority of patients were MSM (95%) and the median age was 36 years. Researchers found that 36% of patients with syphilis were HIV-positive and 42.8% of patients had a prior history of syphilis.

Findings from the questionnaires showed that the median number of sexual contacts in the past 12 months was 10. In addition, 72.5% of patients practiced condomless anal sex, 50.6% engaged in group sex, and 54.7% consumed drugs before or during sex.

All patients with HIV were MSM. Compared with patients without HIV, patients with HIV had more anonymous sex contacts (P =.041), receptive anal sex (P =.011), condomless anal sex (P =.002), group sex (P <.001), and took drugs before or during sex (P <.001).

In the multivariate analysis, patients with HIV and syphilis were more likely to have previous syphilis (adjusted odds ratio [aOR], 4.81; 95% CI, 2.88-8.15), previous Neisseria gonorrhoeae infection (aOR, 3.8; 95% CI, 2.28-6.43), and practice serosorting (aOR 20.4; 95% CI, 7.99-60.96).

Clinically, secondary syphilis was the most common stage in patients with HIV (61.9%). After adjusting for a previous history of syphilis, secondary syphilis remained more common in patients with HIV. In addition, anal chancres were more common in patients with vs without HIV (41.2% vs 17.0%; P =.049).

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Researchers found a high diversity of T pallidum strains; thus, molecular typing did not conclusively explain clinical presentation.

While the findings from this study are specific to a patient population in Barcelona, researchers concluded that “HIV positive patients practicing receptive anal sex and seropositioning may cause them to have anal chancres more often than HIV-negative patients…and provide important information to be considered for public health interventions, including [sexually transmitted infection] screening and, access to health services and risk-reduction programs targeting high-risk groups.”


Arando M, Fernandez-Naval C, Mota-Foix M, et al. Early syphilis: risk factors and clinical manifestations focusing on HIV-positive patients. BMC Infect Dis. 2019;19(1):727.