Mycoplasma genitalium (MG) is an emerging sexually transmitted infection (STI) that is potentially
associated with reproductive tract sequelae in women. This study aimed to estimate MG incidence and treatment
failure and provide estimates of organism load in infection.
Methods. 1110 women aged 16?25 years were recruited from primary care clinics in Australia. Women were
tested for MG at baseline, 6 months, and 12 months, and MG organism load was measured by quantitative polymerase
chain reaction (PCR). MG-positive cases were screened for MG 23S ribosomal RNA (rRNA) gene point
mutations shown to confer azithromycin resistance using high-resolution melt following PCR.
Results. MG incidence rate was 1.3 per 100 person-years (n = 14; 95 confidence interval [CI], .8?2.3);
women reporting 3 or more sex partners in the last 12 months had an increased rate of incident infection (rate
ratio [RR], 5.1; 95 CI, 1.3?19.6]). There were 3 cases of MG reinfection (0.8 per 100 person-years [95 CI,
.1?.9]. Organism load was higher for prevalent than incident infection (P = .04). There were 3 cases of treatment
failure (9.4 [95 CI, 2.0?25.0]); organism load was higher in cases with treatment failure than in successfully
treated cases (P <.01). An MG 23S rRNA mutation was detected in 5 cases (3 cases of treatment failure and 2
Conclusions. Although MG incidence was relatively low, testing should be recommended for women considered
to be at increased risk based on sexual history. Our results also suggest that organism load might be important
in azithromycin treatment failure.