BackgroundThis study aimed to estimate rates of chlamydia incidence and re-infection and to investigate the dynamics of chlamydia organism load in prevalent, incident and re-infections among young Australian women.Methods1,116 women aged 16 to 25 years were recruited from primary care clinics in Australia. Vaginal swabs were collected at 3 to 6 month intervals for chlamydia testing. Chlamydia organism load was measured by quantitative PCR.ResultsThere were 47 incident cases of chlamydia diagnosed and 1,056.34 person years of follow up with a rate of 4.4 per 100 person years (95% CI: 3.3, 5.9). Incident infection was associated with being aged 16 to 20 years [RR = 3.7 (95%CI: 1.9, 7.1)], being employed [RR = 2.4 (95%CI: 1.1, 4.9)] and having two or more new sex partners [RR = 5.5 (95%CI: 2.6, 11.7)]. Recent antibiotic use was associated with a reduced incidence [RR:0.1 (95%CI: 0.0, 0.5)]. There were 14 re-infections with a rate of 22.3 per 100 person years (95%CI: 13.2, 37.6). The median time to re-infection was 4.6 months. Organism load was higher for prevalent than incident infections (p<0.01) and for prevalent than re-infections (p<0.01).ConclusionsChlamydia is common among young women and a high proportion of women are re-infected within a short period of time, highlighting the need for effective partner treatment and repeat testing. The difference in organism load between prevalent and incident infections suggests prevalent infection may be more important for ongoing transmission of chlamydia.

Background: Differences in the determinants of Chlamydia trachomatis ('chlamydia') and Mycoplasma genitalium (MG) genital infection in women are not well understood.

BackgroundTo determine prevalence and incidence of bacterial vaginosis (BV) and risk factors in young sexually-active Australian women.Methods1093 women aged 16–25 years were recruited from primary-care clinics. Participants completed 3-monthly questionnaires and self-collected vaginal smears 6-monthly for 12-months. The primary endpoint was a Nugent Score = 7–10 (BV) and the secondary endpoint was a NS = 4–10 (abnormal flora [AF]). BV and AF prevalence estimates and 95% confidence intervals (95%CI) were derived, and adjusted odds ratios (AOR) calculated to explore epidemiological associations with prevalent BV and AF. Proportional-hazards regression models were used to examine factors associated with incident BV and AF.ResultsAt baseline 129 women had BV [11.8% (95%CI: 9.4–14.2)] and 188 AF (17.2%; 15.1–19.5). Prevalent BV was associated with having a recent female partner [AOR = 2.1; 1.0–4.4] and lack of tertiary-education [AOR = 1.9; 1.2–3.0]; use of an oestrogen-containing contraceptive (OCC) was associated with reduced risk [AOR = 0.6; 0.4–0.9]. Prevalent AF was associated with the same factors, and additionally with >5 male partners (MSP) in 12-months [AOR = 1.8; 1.2–2.5)], and detection of C.trachomatis or M.genitalium [AOR = 2.1; 1.0–4.5]. There were 82 cases of incident BV (9.4%;7.7–11.7/100 person-years) and 129 with incident AF (14.8%; 12.5–17.6/100 person-years). Incident BV and AF were associated with a new MSP [adjusted rate ratio (ARR) = 1.5; 1.1–2.2 and ARR = 1.5; 1.1–2.0], respectively. OCC-use was associated with reduced risk of incident AF [ARR = 0.7; 0.5–1.0].ConclusionThis paper presents BV and AF prevalence and incidence estimates from a large prospective cohort of young Australian women predominantly recruited from primary-care clinics. These data support the concept that sexual activity is strongly associated with the development of BV and AF and that use of an OCC is associated with reduced risk.

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.