Clinical outcomes of syphilis in HIV-negative and HIV-positive MSM: occurrence of repeat syphilis episodes and non-treponemal serology responses

OBJECTIVES

HIV-positive men who have sex with men (MSM) may be at a higher risk of repeat syphilis, have different clinical manifestations and have a different serological response to treatment compared with HIV-negative MSM. The objective of this study was to assess whether HIV-negative and HIV-positive MSM with infectious syphilis (primary, secondary or early latent) differed in history of previous syphilis episodes, disease stage and non-treponemal titre of initial and repeat episodes, and the titre response 6 and 12 months after treatment. Furthermore, determinants associated with an inadequate titre response after treatment were explored.

METHODS

This retrospective analysis used data of five longitudinal studies (four cohorts; one randomised controlled trial) conducted at the STI clinic in Amsterdam, the Netherlands. Participants were tested for syphilis and completed questionnaires on sexual risk behaviour every 3-6 months. We included data of participants with ≥1 syphilis diagnosis in 2014-2019. Pearson's χ² test was used to compare HIV-negative and HIV-positive MSM in occurrence of previous syphilis episodes, disease stage of initial and repeat syphilis episode and non-treponemal titre treatment responses.

RESULTS

We included 355 participants with total 459 syphilis episodes. HIV-positive MSM were more likely to have a history of previous syphilis episodes compared with HIV-negative MSM (68/90 (75.6%) vs 96/265 (36.2%); p<0.001). Moreover, HIV-positive MSM with repeat syphilis were less often diagnosed with primary syphilis (7/73 (9.6%) vs 36/126 (28.6%)) and more often diagnosed with secondary syphilis (16/73 (21.9%) vs 17/126 (13.5%)) and early latent syphilis (50/73 (68.5%) vs 73/126 (57.9%)) (p=0.005). While not significantly different at 12 months, HIV-negative MSM were more likely to have an adequate titre response after 6 months compared with HIV-positive MSM (138/143 (96.5%) vs 66/74 (89.2%); p=0.032).

CONCLUSIONS

In repeat syphilis, HIV infection is associated with advanced syphilis stages and with higher non-treponemal titres. HIV infection affects the serological outcome after treatment, as an adequate titre response was observed earlier in HIV-negative MSM.

Looking at the positives: proactive management of STIs in people with HIV

Patients who are HIV-positive and co-infected with other sexually transmitted infections (STIs) are at risk of increased morbidity and mortality. This is of clinical significance. There has been a dramatic increase in the incidence of STIs, particularly syphilis, gonorrhoea, Mycoplasma genitalium and hepatitis C virus (HCV) in HIV-positive patients. The reasons for this are multifactorial, but contributing factors may include effective treatment for HIV, increased STI testing, use of HIV pre-exposure prophylaxis and use of social media to meet sexual partners. The rate of syphilis-HIV co-infection is increasing, with a corresponding increase in its incidence in the wider community. HIV-positive patients infected with syphilis are more likely to have neurological invasion, causing syndromes of neurosyphilis and ocular syphilis. HIV infection accelerates HCV disease progression in co-infected patients, and liver disease is a leading cause of non-AIDS-related mortality among patients who are HIV-positive. Since several direct-acting antivirals have become subsidised in Australia, there has been an increase in treatment uptake and a decrease in HCV viraemia in HIV-positive patients. The incidence of other sexually transmitted bacterial infections such as Neisseria gonorrhoeae and M. genitalium is increasing in HIV patients, causing urethritis, proctitis and other syndromes. Increasing antimicrobial resistance has also become a major concern, making treatment of these infections challenging. Increased appropriate testing and vigilant management of these STIs with data acquisition on antimicrobial sensitivities and antimicrobial stewardship are essential to prevent ongoing epidemics and emergence of resistance. Although efforts to prevent, treat and reduce epidemics of STIs in patients living with HIV are underway, further advances are needed to reduce the significant morbidity associated with co-infection in this patient setting.

Syphilis: a fresh look at an old foe

Syphilis remains a pressing public health problem globally across different populations including men who have sex with men and pregnant women. It is timely to review what international surveillance data tell us and the evidence behind public health interventions aimed at controlling syphilis. A reinvigorated response to the re-emergence of syphilis is required.