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Abstract
Objectives To investigate the prevalence of the genital mollicutes, Mycoplasma genitalium (MG), Mycoplasma hominis (MH), Ureaplasma urealyticum (UU) and Ureaplasma parvum (UP), and their associations with cervicitis in a sexually transmitted infection (STI) clinic population. Clinical correlates of MG infection were also assessed.
Methods 527 women were enrolled in a cross-sectional study at two STI clinics in Sydney between June 2006 and January 2010. Genital mollicutes were detected by multiplex PCR testing of cervical swabs, and associations with cervicitis were analysed. Cervicitis was defined as >30 polymorphonuclear cells per high-power field in at least three non-adjacent fields of cervical mucus on Gram stain.
Results MG was found in 4.0% of women, MH in 17.1%, UU in 14.1%, and UP in 51.8%. MG was the only mollicute associated with cervicitis (unadjusted prevalence ratio (PR) 1.85, 95% CI 1.52 to 2.26, p<0.0001), and this association remained after adjustment for Chlamydia trachomatis (CT) infection (adjusted PR 1.24 (95% CI 1.04 to 1.48), p=0.02). MG was significantly associated with women being HIV positive (p=0.03), but not with age, vaginal discharge, commercial sex work, being of culturally and linguistically diverse background, or concurrent CT infection. Two of the 21 women with MG had ectopic pregnancies.
Conclusions The authors recommend wider application of PCR testing for MG in STI services, particularly in high-risk women and those with cervicitis or HIV infection.
- Mycoplasma genitalium, Cervicitis, HIV
- mycoplasmas, reproductive health
- women
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Introduction
Increasing evidence is emerging implicating Mycoplasma genitalium (MG) as a genital tract pathogen.1–5 However, the potentially pathogenic roles of other genital mollicutes, Mycoplasma hominis (MH), Ureaplasma urealyticum (UU) and Ureaplasma parvum (UP), are less well characterised.1 MG has been associated with cervicitis1–3 endometritis1 4 and pelvic inflammatory disease.1 5
The objectives of this study were to determine the population prevalence of MG, MH, UU and UP and their associations with cervicitis, and to examine clinical correlates of MG.
Methods
A cross-sectional study was undertaken in two urban Sydney sexually transmitted infection (STI) clinics from June 2006 to January 2010. Ethics approval was granted by South Eastern Sydney and Illawarra Area Health Service human research ethics committee and Sydney South West Area Health Service ethics committee.
Participant selection
A total of 527 consecutive eligible consenting women were enrolled, with 83% recruited from a primary site. Both sites are part of a network of public STI clinics in urban Sydney servicing the same priority populations and are HIV referral centres. Inclusion and exclusion criteria and sample collection have previously been described.6 Of 570 eligible women, 527 consented (92.5%). All women had cervical swabs tested for MG, MH, UU, UP and Chlamydia trachomatis (CT). Cervicitis was defined as >30 polymorphonuclear cells per high-power field in at least three non-adjacent fields of cervical mucus on Gram stain. Clinicians' cervical Gram stains for case definition of cervicitis were later read by a single laboratory scientist blinded to clinical diagnosis.
Nucleic acid extraction and PCR amplification
Specimens were extracted within 48 h of receipt, stored, and subsequently tested in batches. Nucleic acid extraction was carried out using a robotic extraction machine (MagNAPure LC; Roche, Mannheim, Germany) applying the ‘Total NA’ protocol.
Detection of the mollicutes MG, MH, UP and UU involved a single-round multiplex PCR (mPCR) (VDL06) followed by PCR ELISA. The VDL06 mPCR was carried out as described,6 except reagents from the iScript One-Step RT-PCR kit (BioRad, Hercules, California, USA) were used for amplification. The sensitivity of VDL06 mPCR has been described previously.6 The specificity was determined by DNA sequencing of the first 10 positive samples of each mollicute from the study, and resulted in 100% specificity. Chlamydia testing was performed in a NATA-accredited diagnostic laboratory, using a commercial assay (COBAS Amplicor CT/NG multiplate ELISA; Roche) following the manufacturer's instructions.
Statistical methods
Associations of mollicutes and CT with cervicitis were estimated using prevalence ratios (PRs), 95% CIs and p values. Given that the study was cross-sectional and cervicitis is common, we calculated PRs rather than ORs. Multivariate analysis in logistic regression models involved forward selection including only covariates with p<0.05. MG correlates were examined using χ2 tests and t tests. All analyses were performed with SAS V9.2.
Results
The prevalence of the mollicutes was: MG, 4.0%; MH, 17.1%; UU, 14.1%; UP, 51.8%. CT prevalence was 5.7%. MG was the only mollicute associated with cervicitis (unadjusted PR 1.85, 95% CI 1.52 to 2.26, p<0.0001), and this association remained after adjustment for CT (adjusted PR 1.24 (95% CI 1.04 to 1.48), p=0.02) (table 1).
Associations of infectious exposures with cervicitis
MG was significantly associated with HIV positivity. Two of the 21 women with MG were HIV positive (9.5%) compared with 11 of 506 women without MG (2.2%) (p=0.03). There was no association between MG and age (p=0.28), vaginal discharge (p=0.32), commercial sex work (p=0.67), being culturally and linguistically diverse (p=0.95), or concurrent CT infection (p=0.44). Two of the 21 women with MG had an ectopic pregnancy.
Mollicutes were found in 346/527 (65.7%) women, and, of these, 95 (27.5%) had more than one species. UP occurred significantly more often as a single infection (72% of UP infections) (p<0.0001) in contrast with the other mollicutes, which were more likely to coexist with other species.
The prevalence of cervicitis was 47.7%. Agreement between the clinician and laboratory scientists' Gram stain diagnosis of cervicitis was 92.8% (κ estimate 85.4%).
Discussion
In this study of an STI clinic female population, the prevalence of MG was 4.0%. This is similar to other high-risk populations: 6.3% in a Swedish STI population2 and 4.5% in a Norwegian STI clinic setting,7 but lower than 8.7% in women having abortions in New Zealand.8 Importantly, the prevalence of MG was similar to that of Chlamydia, also noted in other STI clinic populations.2 3 9
MG was the only mollicute significantly associated with cervicitis in this study. Evidence concerning the role of MG in cervicitis is conflicting.1–3 10 Studies of associations of ureaplasmas and MH with cervicitis are also inconclusive.1 The prevalence of cervicitis in this study was high (47.7%), as noted in other STI clinic populations.1 7
MG was significantly associated with HIV positivity (p=0.03). This association was also found in a study of West African commercial sex workers.3 As HIV shedding is associated with high MG organism burden,10 MG infection may facilitate HIV transmission. We did not find an association of MG with concurrent CT infection, consistent with other studies,2 8 but not with Huppert et al,9 who found an association in adolescent women.
Interestingly, two women with MG had ectopic pregnancies within 1 month of study enrolment. As these data were not specifically sought in all participants, we are unable to evaluate the significance of this. It may be a chance finding, but warrants further investigation.
UP was very common (52%) and was usually found as a single mollicute infection. This raises the possibility of a potential probiotic effect of UP with respect to other mollicutes.
As this study involves a high-risk population, its applicability to general populations is limited. In addition, sample size was too small to detect weak associations. Strengths of the study include robust case definition for cervicitis and high participation rate in a consecutive series of women.
In conclusion, we found that MG was the only mollicute species significantly associated with cervicitis, and MG was associated with HIV positivity. We recommend wider application of PCR testing for MG in STI services.
Key messages
Prevalence in women of Mycoplasma genitalium (MG) was 4.0%, Mycoplasma hominis 17.1%, Ureaplasma urealyticum 14.1%, and Ureaplasma parvum 51.8%.
MG was the only mollicute associated with cervicitis, and this association remained after adjustment for Chlamydia trachomatis infection.
MG was associated with HIV positivity, but not with age, vaginal discharge, commercial sex work, culturally and linguistically diverse background or concurrent chlamydia.
We recommend wider application of PCR testing for MG in STI services, particularly in high-risk women and those with cervicitis or HIV infection.
Acknowledgments
Staff and patients of the Short Street Centre and RPA Sexual Health. Christa McPherson, Laboratory Scientist, SEALS Laboratory, St George Hospital for Gram stain interpretation. William Paauwe for assistance with IT and database management. Christopher J McIver, Michael Fennell and the Virology Diagnostic Laboratory SEALS Microbiology, for assistance with PCR testing.
Footnotes
Funding MJL was in part supported by a scholarship from Novartis, HIV and Related Projects (HARP) Unit, South East Sydney and Illawarra Area Health Service, Sydney, NSW, Australia.
Competing interests None.
Ethics approval This study was conducted with the approval of the South Eastern Sydney and Illawarra Area Health Service human research ethics committee and the Sydney South West Area Heath Service ethics review committee (Royal Prince Alfred Hospital Zone).
Provenance and peer review Not commissioned; externally peer reviewed.