Background
Mycoplasma genitalium (MG) causes 15-25% of nongonococcal urethritis cases in men. Antibiotic resistance limits treatment options. Doxycycline reduces bacterial load but is only 30-40% effective against MG, and is first in sequential treatment algorithms. Few studies have evaluated the impact of doxycycline post-exposure prophylaxis (doxy-PEP) on MG infection.
Methods
MG prevalence and incidence and clearance over ≤12 months were evaluated in a convenience sample of DoxyPEP trial participants (ppts). Men who have sex with men (MSM) and transgender women (TGW) with HIV or on PrEP were randomized 2:1 to doxy-PEP or standard of care (SOC) to assess impact on bacterial STI incidence. Urine and rectal swabs, collected at enrollment and quarterly visits regardless of symptoms, were tested with the Hologic Aptima MG molecular test. Results were not released. In ppts with MG testing at ≥2 visits, time to MG incidence and clearance was compared between doxy PEP and SOC groups using interval-censored survival analysis.
Results
585 study ppts, 30.6% with HIV, submitted ≥2 MG specimens. STI diagnoses in the year before enrollment were 67.0% with GC, 59.3% CT, and 19.0% syphilis. At enrollment, ppts reported a median of 9 (IQR 4, 18) sexual partners in the prior 3 months. During follow-up, they reported a median 18 (IQR 6, 34) doses of doxy-PEP per study quarter. Baseline urogenital MG prevalence was 7% in the SOC arm and 6% in the doxy-PEP arm, rectal MG was 14% and 16%, respectively; prevalence was similar by HIV status. Among ppts without MG infection at enrollment, urogenital incidence of MG was 1.10 per 100 person-years (100PY) in SOC and 0.86 in the doxy-PEP arm (HR 0.76, 95% CI 0.08, 7.32). Rectal incidence was 25.8 and 17.0, respectively (HR 0.72, 95% CI 0.44, 1.16). In ppts with urogenital MG at enrollment, clearance rate in SOC (43.5/100PY) was lower than the doxy-PEP arm (108.5/100PY, HR 3.48, 95% CI 1.02, 11.89, p = 0.046). Rectal clearance rate was 100.8 and 126.9, respectively (HR 1.48, 95% CI 0.78, 2.81).
Conclusions
MG incidence and prevalence were modestly lower than previous estimates in similar populations of MSM and TGW with high STI risk. In this study with limited events, MG incidence effect estimates were similar to the DOXYVAC study but not statistically significant. The clearance rate of urogenital MG, but not rectal MG, was significantly higher in the doxy-PEP arm. The impact of doxy-PEP on MG incidence and clearance at urogenital and rectal sites warrants further study.
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