Background Mycoplasma genitalium is a sexually transmitted infection (STI) associated with cervicitis, endometritis and pelvic inflammatory disease in women. There is a lack of data on M.genitalium in the United Kingdom. We conducted a study to determine its prevalence and risk factors among sexually active young women in the general population and attending STI clinics.

Methods First catch urine samples, self-taken vaginal and cervical swabs from 4644 women in the National Chlamydia Screening Programme (NCSP) and attending two London STI clinics were tested for M. genitalium by quantitative real-time PCR, confirmed by MgPa 1–3 genotyping. C.trachomatis results, demographic, sexual behaviour (NCSP only, 2470 women) and STI (clinics only, 2174 women) data were also available.

Results M. genitalium prevalence was 3%, C.trachomatis 5% and only 0.5% of women were co-infected. M.genitalium was more prevalent in swab than urine samples (4.6% vs. 1.4%, p < 0.001) with a significantly higher mean bacterial load. Among NCSP participants M.genitalium was associated with ethnicity (black 4.7% vs. white 2%, p = 0.01) and C.trachomatis with age (16–19 years 8.5% vs. 20–24 years 5.7%, p < 0.01). M.genitalium and C.trachomatis were detected more frequently in women reporting multiple sexual partners in the previous year compared to women who reported only one partner (OR 2.2, p = 0.02 and OR 1.8, p < 0.01, respectively). Among STI clinic attendees M.genitalium was associated with younger age (16–19 years 9.9%, 20–24 years 6.2% vs. > 25 years 1.7%, p = < 0.01). Chlamydia prevalence was 6% in STI clinic attendees aged 16–24. Women previously diagnosed with chlamydia or Trichomonas vaginalis were significantly more likely to have M.genitalium compared to women with no previous STI diagnoses (OR 2.4, p = 0.02 and OR 5.7, p < 0.01, respectively).

Conclusion M. genitalium and C. trachomatis seldom co-exist and appear to have different risk factors. Further data on M.genitalium are necessary to determine the need for routine testing and treatment.