Aetiology and prevalence of mixed-infections and mono-infections in non-gonococcal urethritis in men: a case-control study

Sex Transm Infect. 2020 Jun;96(4):306-311. doi: 10.1136/sextrans-2019-054121. Epub 2019 Sep 12.


Objectives: Chlamydia trachomatis (CT) and Mycoplasma genitalium (MG) cause the majority of non-gonococcal urethritis (NGU). The role of Ureaplasma urealyticum (UU) in NGU is unclear. Prior case-control studies that examined the association of UU and NGU may have been confounded by mixed infections and less stringent criteria for controls. The objective of this case-control study was to determine the prevalence and aetiology of mixed infections in men and assess if UU monoinfection is associated with NGU.

Methods: We identified 155 men with NGU and 103 controls. Behavioural and clinical information was obtained and men were tested for Neisseria gonorrhoeae and CT, MG, UU and Trichomonas vaginalis (TV). Men who were five-pathogen negative were classified as idiopathic urethritis (IU).

Results: Twelve per cent of NGU cases in which a pathogen was identified had mixed infections, mostly UU coinfections with MG or CT; 27% had IU. In monoinfected NGU cases, 34% had CT, 17% had MG, 11% had UU and 2% had TV. In controls, pathogens were rarely identified, except for UU, which was present in 20%. Comparing cases and controls, NGU was associated with CT and MG monoinfections and mixed infections. UU monoinfection was not associated with NGU and was almost twice as prevalent in controls. Men in both the case and control groups who were younger and who reported no prior NGU diagnosis were more likely to have UU (OR 0.97 per year of age, 95% CI 0.94 to 0.998 and OR 6.3, 95% CI 1.4 to 28.5, respectively).

Conclusions: Mixed infections are common in men with NGU and most of these are UU coinfections with other pathogens that are well-established causes of NGU. UU monoinfections are not associated with NGU and are common in younger men and men who have never previously had NGU. Almost half of NGU cases are idiopathic.

Keywords: chlamydia infection; chlamydia trachomatis; epidemiology (general); mycoplasma; urethritis.

Publication types

  • Research Support, N.I.H., Extramural

MeSH terms

  • Adolescent
  • Adult
  • Case-Control Studies
  • Chlamydia trachomatis / isolation & purification*
  • Coinfection / epidemiology*
  • Coinfection / etiology
  • Humans
  • Male
  • Middle Aged
  • Mycoplasma genitalium / isolation & purification*
  • Neisseria gonorrhoeae / isolation & purification
  • Prevalence
  • Trichomonas vaginalis / isolation & purification*
  • Ureaplasma urealyticum / isolation & purification*
  • Urethritis / epidemiology*
  • Urethritis / etiology
  • Young Adult