Background Commercial sex workers (CSW) are particularly exposed to sexually transmitted infections (STI). To direct prevention measures, we estimated the prevalence of the three most common bacterial STI (chlamydia, gonorrhoea and syphilis) and examined factors associated with infection among CSW visiting an STI-clinic in the Netherlands.

Methods A CSW was defined as a person exchanging sex for money or other valuable goods in the past 6 months prior to the consultation. Using 2006–2011 national surveillance data on STI clinic visits, we estimated the prevalence of consultations with at least one STI (positive laboratory test for chlamydia, gonorrhoea and/or syphilis). We used univariable and multivariable logistic regression to identify factors associated with these STI, stratified by gender.

Results Between 2006 and 2011, the prevalence of bacterial STI was 9% among 23,825 female sex workers (FSW) and 18% among 2,353 male sex workers (MSW) consultations. Young CSW (15–24 years) had a higher prevalence (27% for MSW, 16% for FSW) than CSW aged > = 25 years (15% for MSW, 7% for FSW, p < 0.0001). Prevalence of STI was higher among MSW having sex with men than among heterosexual MSW (OR = 1.9 95% CI: 1.4–2.5). MSW who already knew their HIV positive status and MSW who were diagnosed as HIV positive during the consultation had a higher prevalence than those who were tested negative for HIV (OR = 4.8 95% CI: 2.8–8.2 and OR = 3.4 95% CI: 2.3–4.9 respectively).

Conclusions Young male and female CSW, MSW having sex with men and known HIV-positive MSW had a higher prevalence of STI. Prevention activities need to target young sex workers to increase early diagnosis, prevention and treatment. MSW having sex with men and those known HIV positive may require more targeted interventions.