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Mycoplasma genitalium in asymptomatic patients: implications for screening
  1. J D C Ross1,
  2. L Brown1,
  3. P Saunders2,
  4. S Alexander2
  1. 1
    Whittall Street Clinic, Birmingham, UK
  2. 2
    Sexually Transmitted Bacteria Research Laboratory, Health Protection Agency, Centre for Infections, Colindale, London, UK
  1. Correspondence to Professor J D C Ross, Whittall Street Clinic, Whittall Street, Birmingham B4 6DH, UK; jonathan.ross{at}hobtpct.nhs.uk

Abstract

Objectives: Mycoplasma genitalium is well established as a cause of urethritis and has also been associated with cervicitis, endometritis and pelvic infection. Low rates of infection suggest screening may be inappropriate in the general population, but it remains unclear whether asymptomatic patients attending a sexual-health clinic should be tested routinely. The objective of this study was to measure the positivity rate of M genitalium infection in asymptomatic individuals presenting to a sexual-health clinic to inform the need for screening in this population.

Methods: Asymptomatic patients were identified using a structured questionnaire and tested for M genitalium from genital swabs or urine using two separate polymerase chain reaction (PCR) assays incorporating different primer sequences.

Results: 1304 patients were approached over a 6-month period. 743 (57%) patients were symptomatic, and 168 (13%) refused consent, leaving 394 (30%) patients who entered the study. Residual samples were available for 308 (79%) patients, 168 (54%) men and 140 (46%) women. 14/308 (4.5%, 95% CI 2.2 to 6.9%) asymptomatic patients were infected with M genitalium, and an additional 2 (0.6%, 95% CI 0.2 to 2.3%) patients had discrepant PCR results. No significant associations were found between M genitalium infection and age, gender, ethnicity or isolation site.

Conclusion: The positivity rate of M genitalium infection in asymptomatic sexual-health clinic attendees is comparable with that of gonorrhoea or chlamydia, and, if evidence of pathogenicity continues to accumulate, a further assessment of the role of routine screening in this setting would be appropriate.

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Mycoplasma genitalium is a small bacterium which is recognised as a cause of urethritis, cervicitis and endometritis.1 2 Upper-genital-tract involvement in women is also likely, with a reported association between M genitalium and tubal factor infertility,3 the isolation of the organism from endometrium and the fallopian tube,4 and the inoculation of M genitalium leading to salpingitis in non-human primates.5 Measuring the positivity rate of asymptomatic infection with M genitalium in patients attending sexual-health clinics is needed to help determine whether testing for M genitalium should be included within routine screening tests to exclude STIs in this setting.

The primary objective of this study was to measure the positivity rate of M genitalium in asymptomatic men and women attending a sexual-health clinic in the UK.

Methods

A convenience sample of asymptomatic sexual-health clinic attendees were approached to participate in the study. A paper-based self-administered questionnaire was used to determine whether patients had any genital-tract-related symptoms, and asymptomatic individuals were approached to participate in the study.

Study participants were randomised to have either a physician-/nurse-taken genital swab (men—urethral swab, women—cervical swab) or a self-taken specimen (men—urine, women—vulval swab). Male urine samples and female self-taken vulval swabs were collected in Roche chlamydia polymerase chain reaction (PCR) media. Female cervical swabs and male urethral swabs were collected in Becton-Dickinson (Mountain View, California) chlamydia strand displacement amplification (SDA) media.

A more detailed description of the methodology is available in the web appendix.

Results

A total of 1304 patients were approached over a 6-month period in 2006; 743 (57%) patients were symptomatic, and 168 (13%) refused consent, leaving 394 (30%) patients who entered the study. Residual samples were available for 308 (78%) patients. The patient characteristics, specimen distribution and history of STI for those entering the study are shown in the web appendix.

Fourteen (4.5%, 95% CI 2.2 to 6.9%) patients were positive for M genitalium on both the MgPa and Mg219 PCRs, two (0.6%, 95% CI 0.2 to 2.3%) patients were positive only on the MgPa PCR, and 292 (94.8%, 95% CI 92 to 97%) patients were negative on both PCRs.

The associations between infection with M genitalium and patient demographics, concurrent STI, type of specimen tested and past history of STI are shown in table 1. A significant association was found between Mgenitalium infection and gonorrhoea. However, all five positive gonorrhoea samples were self-taken vulval swabs tested using the Roche Amplicor PCR. Subsequent cervical specimens were taken for N gonorrhoeae culture prior to treatment, of which four were negative, and one was reported as positive. A non-significant trend towards higher rates of mycoplasma infection in women (9/138—6.5%, 95% CI 3.5 to 11.9%) compared with men (5/168—3%, 95% CI 1.3 to 6.8%) was also noted.

Table 1

Associations with Mycoplasma genitalium infection in asymptomatic genitourinary medicine-clinic attendees

M genitalium isolation rates between clinical specimens were: male urine 2/84 (14%), male urethral swab 3/84 (21%), female vulval swab 6/59 (43%) and female cervical swab 3/79 (22%).

Conclusions

A positivity rate of M genitalium of 4.5% (95% CI 2.2 to 6.9%) was found in asymptomatic patients attending a sexual-health clinic, with a non-significant trend towards higher rates of infection in women

Genitourinary medicine clinics in the UK perform over 1.5 million tests for STIs per year and do not currently screen routinely for M genitalium. The largest previous study of STI clinic attendees examined 353 men without urethritis and reported a prevalence of 0.8%, although symptoms or signs other than those associated with urethritis were not reported.6 A total of 81 patients from three additional studies detected only six infections in asymptomatic clinic attendees.7 8 9 Our positivity estimate may provide a more accurate measure reflecting a large sample size, inclusion of male and female patients, use of a well-validated assay, confirmatory testing and a systematic approach to screening for asymptomatic infection prior to testing.

In the same clinic population, and over the same time period, the positivity rate of gonorrhoea was 264/7820 (3.4%) and for chlamydia 766/7820 (9.8%), and screening for both these infections is recommended in asymptomatic attendees at UK sexual-health clinics.10 Before making a clear recommendation on screening for mycoplasma, a further assessment of the risk and consequences of pelvic infection in untreated women is required. In addition, a commercially available, validated and reasonably priced test for M genitalium is a prerequisite to wider implementation of screening or testing. As more information on the pathogenesis of the infection becomes available, this study supports the need to review the role of screening for M genitalium infection in asymptomatic sexual-health clinic attendees.

Acknowledgments

We thank V Chalker for technical advice and guidance.

Author contributions: JR was responsible for study concept, design, supervision and manuscript preparation; LB was responsible for study design, data collection, supervision and manuscript review; PM was responsible for laboratory testing and manuscript review; SA was responsible for laboratory testing, manuscript preparation and manuscript review.

REFERENCE

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Footnotes

  • An appendix is published online only at http://sti.bmj.com/content/vol85/issue6

  • Funding Heart of Birmingham tPCT.

  • Competing interests None.

  • Ethics approval Ethics approval was provided by South Birmingham LREC.

  • Provenance and peer review Not commissioned; externally peer reviewed.

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