Factors affecting vaginal pH levels among female adolescents attending genitourinary medicine clinics.

OBJECTIVES: Vaginal pH is related to hormonal status, and adolescents experience disturbed hormonal patterns following menarche. We assessed hormonal factors and risk of abnormal vaginal pH and bacterial vaginosis (BV) among adolescents attending genitourinary medicine (GUM) clinics. METHODS: In a cross sectional study adolescents within 5 years of menarche, < or =17 years, or with oligo-amenorrhoea were recruited. Vaginal pH and BV were assessed and among those not using hormonal contraceptives, estrone-3-glucuronide (E3G) and pregnanediol-3alpha-glucuronide (P3G) concentrations were measured. RESULTS: Among 102 adolescents, 59.8% (61) had a high vaginal pH (>4.5), which was higher than the prevalence of BV, detected in 33% (34). No association was found between presence of sexually transmitted infections (STI) and vaginal pH. In logistic regression, after controlling for BV and condom use, vaginal pH was positively associated with cervical ectopy (OR = 2.5; 95% CI 1.0 to 6.6, p = 0.05) and STI treatment history (OR = 2.5; 95% CI 0.9 to 6.5, p = 0.07), and negatively associated with use of Depo-Provera (OR = 0.1; 95% CI 0.03 to 0.6, p = 0.003) and recent onset (<12 months) of sexual activity (OR = 0.2; 95% CI 0.1 to 0.7, p = 0.004). Among 23 adolescents not using hormonal contraceptives, a high pH occurred more often in abnormal compared to normal menstrual cycles (OR = 10.8; 95% CI 1.4 to 85.4; p = 0.026). E3G concentrations were inversely correlated with vaginal pH in the follicular phase (Spearman: r = 0.51; p = 0.024). CONCLUSIONS: Ectopy and abnormal menstrual cycles are common features of adolescence. Their presence is associated with increased risk of abnormal pH, and may also predispose to BV.

Biological and hormonal markers of chlamydia, human papillomavirus, and bacterial vaginosis among adolescents attending genitourinary medicine clinics.

OBJECTIVE: To assess maturity indices, menstrual patterns, hormonal factors, and risk of adolescent genital tract infections. METHODS: Cross sectional study in three genitourinary medicine clinics. Females 17 years or less, within 5 years of menarche, or reporting oligo-amenorrhoea were screened for genital tract infections and menstrual cycle characteristics determined. The outcome measures were risk factors associated with chlamydia, human papillomavirus (HPV DNA) and bacterial vaginosis (BV), separately and pooled. Correlations between estrone-3-glucuronide (E3G) and pregnanediol-3alpha-glucuronide (P3G) hormone concentrations and chlamydia, HPV, and BV. RESULTS: Among 127 adolescents, HPV was present in 64.4% (95% CI: 54.5 to 74.3), BV in 33.9% (19.1 to 34.5), and chlamydia in 26.8% (19.1 to 34.5). Breast maturity, oligomenorrhoea, and older gynaecological age were associated with lower risk of all infections. After adjustment for calendar age, race, and behavioural factors, gynaecological age remained significant (OR = 0.7, 0.6-0.9; p = 0.008). Behavioural risk factors differed by infection. Smoking was protective for HPV (OR = 0.1, 0.0 to 0.9; p = 0.007), and a recent new partner for chlamydia (OR = 0.3, 0.1 to 0.9; p = 0.024). Sex during menses was associated with increased BV risk (OR = 3.3, 1.5 to 7.2; p = 0.003). Chlamydia was higher among adolescents who used emergency contraception (2.5; 1.1 to 5.9, p = 0.029) and lower among those using condoms at last sex (OR = 0.3, 0.1 to 0.9; p = 0.015). Among 25 adolescents not using hormonal contraceptives, 15 had disturbed or anovulatory cycles. Chlamydia risk was inversely associated with P3G concentrations (Mann-Whitney; p = 0.05). CONCLUSIONS: Adolescents engaging in high risk behaviour at a young gynaecological age are susceptible to multiple infections. Adolescent clinical assessment should include gynaecological age.

Mixed strain schistosome infections of snails and the evolution of parasite virulence.

Mathematical models often propose that within-host competition between parasites can be a major factor in the evolution of increased parasite virulence. Kin selection predicts that as the coefficient of relatedness between infecting parasites decreases, the benefits of competition to individual genotypes increases. Thus where parasites can adjust their behaviour in response to current conditions, higher virulence is predicted in multiple genotype infections. There is limited experimental data, however, regarding the effects of mixed strain infections on host and parasite fitness. We investigated, for a snail-schistosome system, whether a conditional increase in replication rates occurred in mixed genotype infections and resulted in increased virulence. Four groups of Biomphalaria glabrata snails were exposed to 1 or 2 laboratory strains of Schistosoma mansoni. Mixed genotype infections were observed to be more virulent than single genotype infections, in terms of reductions in host reproductive success and survival. Parasite reproductive rate was also increased in mixed strain groups. Reduced host reproductive success was suggested to be directly due to the genetic heterogeneity of the parasitic infections resulting in increased host defence costs. Reduced host survival was consistent with an adaptive conditional parasite response.