Article Text

Download PDFPDF

Mycoplasma genitalium: an important sexually transmitted infection comes into focus
  1. Joseph D Tucker1,2,3,
  2. Jason J Ong1,4,5
  1. 1 Social Entrepreneurship to Spur Health (SESH) Global, Guangzhou, China
  2. 2 University of North Carolina, Chapel Hill, North Carolina, USA
  3. 3 Infectious and Tropical Diseases, London School of Hygiene and Tropical Medicine, London
  4. 4 Department of Global Health and Development, London School of Hygiene and Tropical Medicine, London, UK
  5. 5 Central Clinical School, Monash University, Melbourne, Victoria, Australia
  1. Correspondence to Dr Joseph D Tucker, University of North Carolina Chapel Hill Project-China, Guangzhou 510095, China; jdtucker{at}med.unc.edu

Statistics from Altmetric.com

Invited commentary

The bacterium Mycoplasma genitalium is frequently asymptomatic but can cause urethritis in men, and cervicitis, endometritis, pelvic inflammatory disease and infertility in women.1 2 Our understanding of this infection has rapidly expanded since it was first described at a British genitourinary medicine clinic nearly three decades ago.3 Biological and diagnostic issues have likely contributed to the blurriness surrounding this STI—it lacks a cell wall (and so is not visualised with routine Gram stain) and the fastidious organism requires 1–2 months to culture. In addition, the limited number of commercially available diagnostic tests has restricted testing and extensive epidemiological investigation. Currently, no routine serological diagnostics exist for M. genitalium and there are no US Food and Drug Administration-approved diagnostics. This daunting biology and diagnostic situation begs the question: why does detecting this pathogen matter when most empirical therapy covers the bacteria?

Two changes have sharpened the focus on M. genitalium in recent years—greater availability of nucleic acid amplification test (NAAT)-based diagnostic testing and the rise of antibiotic resistance. From a diagnostic perspective, there are now widely accessible NAAT diagnostics that can conveniently and rapidly test samples from multiple sites—first-void urine, and swabs from the anorectum, endocervix, urethra and vagina. NAAT diagnostics are used for research purposes and have received regulatory approval from the European Union.4 From the perspective of antibiotic resistance, macrolide resistance is increasingly common among patients with M. genitalium infection.5 Rising treatment failure associated with fluoroquinolone treatment has also been reported.6

The increase in NAAT diagnostics and antibiotic resistance have inspired greater M. genitalium epidemiology studies that are gathered in the systematic review and meta-analysis by Baumann et al.7 This systematic review pored over 3000 citations and identified 117 studies that examined the prevalence of M. genitalium. The authors extracted data from the 63 studies that had at least 500 individuals. To reduce small sample bias, the decision to include only studies with greater than 500 participants was not made lightly—the authors provided an empirical comparison of studies with less than and greater than 500 participants, providing a compelling rationale for the proposed approach.

To our knowledge, this study represents the first systematic review and meta-analysis of M. genitalium prevalence in asymptomatic populations. The review brings together evidence from several large population-representative studies of M. genitalium. There was a higher prevalence of M. genitalium among studies of men who have sex with men (data from five studies, 3.2% prevalence, 95% CI 2.1 to 5.1) and female sex workers (data from four studies, 15.9% prevalence, 95% CI 13.5 to 18.9). They found a lower prevalence of M. genitalium among studies of pregnant women (data from four studies, 0.9% prevalence, 95% CI 0.6 to 1.4). There was also higher M. genitalium prevalence in countries with lower levels of development (data from three studies, 3.9%, 95% CI 2.2 to 6.7) compared with countries with higher levels (data from three studies, 1.3%, 95% CI 1.0 to 1.8).

These exciting data shine a bright light on M. genitalium epidemiology among asymptomatic populations in many settings. Three implications of this systematic review and meta-analysis are worth highlighting related to diagnostic algorithms and guidelines, mathematical modelling and remaining unknowns.

First, this systematic review and some of the included studies can provide useful data for the development of diagnostic algorithms and practice guidelines. Although there are recommendations for optimal clinical management of M. genitalium within STD guidelines in Europe, USA and Australia,8–10 there are no clear diagnostic algorithms for M. genitalium testing. Dr Baumann and colleagues make the important point that universal screening is inappropriate for populations with a low prevalence of M. genitalium—for example, asymptomatic populations in general. However, a more difficult question is to what extent targeted screening of asymptomatic individuals should be considered among groups with a known increased prevalence (eg, female sex workers and men who have sex with men). The data presented in this review will provide useful data for those revising clinical management guidelines for individuals presenting with non-gonococcal urethritis (NGU) .

Second, this study can provide inputs for mathematical modelling studies, as the authors also point out. Mathematical modelling studies have proven valuable in estimating STD transmission and contributed to our knowledge about STD control interventions. But all models require high-quality data in order to generate precise estimates. Further information about M. genitalium incidence, persistence and prevalence stratified by anatomic site of infection would be invaluable for further understanding the mechanisms of transmission. Of importance for future studies is to ensure that testing includes all relevant anatomic sites, otherwise this may lead to underestimation of the infection.11

Finally, while the systematic review provides a strong foundation of evidence, it also suggests substantial gaps in our understanding of M. genitalium epidemiology. For example, the study only identified 11 general population studies of M. genitalium, with six studies in a higher development index category and five studies in a lower development index category. Although there were not sufficient numbers of studies to perform subanalysis based on region, it will be important to undertake M. genitalium research in other countries and regions.

Given greater M. genitalium NAAT availability and rising antibiotic resistance, understanding the prevalence of M. genitalium infection becomes increasingly important. This also provides opportunities for examining the frequency of M. genitalium antibiotic resistance. The systematic review and meta-analysis in this issue of STI is a harbinger of progress. We hope that this evidence will spur further M. genitalium research and programmes.

Acknowledgments

The authors thank Ligang Yang for reviewing an earlier version of this manuscript.

References

Footnotes

  • Handling editor Jackie A Cassell

  • Contributors JDT wrote the first draft and the outline. Both JDT and JJO made substantive contributions, reviewed the final version and approved the manuscript.

  • Funding This research received no specific grant from any funding agency in the public, commercial or not-for-profit sectors.

  • Competing interests None declared.

  • Provenance and peer review Commissioned; internally peer reviewed.

Request Permissions

If you wish to reuse any or all of this article please use the link below which will take you to the Copyright Clearance Center’s RightsLink service. You will be able to get a quick price and instant permission to reuse the content in many different ways.

Linked Articles