Unrestricted partial funding from Frederiksberg Kommune, Frederiksberg, Denmark. BD held an Medical Research Council Population Health Scientist Fellowship (G0902120). KT held an National Institute for Health Research Post-Doctoral Fellowship 2009-02-055.

The aetiology of non-gonococcal urethritis (NGU) remains unexplained in 30-40% of patients. Urine samples from men attending Swedish sexually transmitted disease clinics were examined by species-specific quantitative PCRs for Chlamydia trachomatis, Mycoplasma genitalium, Trichomonas vaginalis, Ureaplasma urealyticum, U. parvum, adenovirus, herpes simplex virus, Neisseria meningitidis, Haemophilus influenzae, Moraxella catarrhalis and Streptococcus pneumoniae. A total of 187 men with acute NGU (symptoms ≤ 30 days) and 24 with chronic NGU (symptoms < 30 days) were cases, and 73 men without NGU were controls. Number of lifetime sexual partners was negatively associated with U. urealyticum bacterial load. C. trachomatis and M. genitalium were associated with NGU, as was U. urealyticum, with bacterial loads ≥ 1.3 × 103 genome equivalents/ml urine. Virus and H. influenzae might explain a few NGU cases, but the aetiology in at least 24% of patients with acute NGU was unexplained. In multivariate analysis, detection of U. urealyticum was significantly more common in acute NGU (20%) compared with controls (11%).

BackgroundNon-gonococcal urethritis (NGU) is a common syndrome in men. NGU may have several causes, but many cases are caused by sexually transmitted infections that may also cause complications in their female partners. Chlamydia trachomatis and Mycoplasma genitalium are the most common causes of NGU, but in up to 35% of the cases, none of the known viral or bacterial causes are found. Traditionally, pathogens have been detected using various culture techniques that may not identify all species present in the urethra. To address this, we used culture-independent methods for analysis of the male urethral microbiota.MethodsThis case-control study analysed first void urine samples, collected at STD clinics in Stockholm, Sweden from men with idiopathic urethritis (IU), i.e. negative for Neisseria gonorrhoeae, Chlamydia trachomatis, Mycoplasma genitalium, Ureaplasma urealyticum, Trichomonas vaginalis, adenovirus, and herpes simplex virus type 1 and -2 together with samples from men without urethritis. Forty-six controls and 39 idiopathic urethritis patients were analysed.ResultsThe microbiota was highly diverse: None of the 302 operational taxonomic units (OTUs) found in negative controls and IU patients were found in all of the samples or even in all of the samples in one group. More than 50% of the OTUs were only found in one or two of the total of 85 samples. Still the most dominant 1/6 of the genera constituted 79% of the sequences.Hierarchical clustering in a heatmap showed no specific clustering of patients or controls.A number of IU patient samples were dominated by a single genus previously related to urethritis (Gardnerella, Haemophilus, Ureaplasma).ConclusionThe male urethra contain a very diverse composition of bacteria, even in healthy controls. NGU may be caused by a number of different bacteria but more studies including a higher number of samples are needed for elucidation of the role of each species.

A novel multiplex quantitative real-time polymerase chain reaction (qPCR) for simultaneous detection of U. urealyticum and U. parvum was developed and compared with quantitative culture in Shepard's 10 C medium for ureaplasmas in urethral swabs from 129 men and 66 women, and cervical swabs from 61 women. Using culture as the gold standard, the sensitivity of the qPCR was 96% and 95% for female urethral and cervical swabs, respectively. In male urethral swabs the sensitivity was 89%. The corresponding specificities were 100%, 87% and 99%. The qPCR showed a linear increasing DNA copy number with increasing colour-changing units. Although slightly less sensitive than culture, this multiplex qPCR assay detecting U. urealyticum and U. parvum constitutes a simple and fast alternative to the traditional methods for identification of ureaplasmas and allows simultaneous species differentiation and quantitation in clinical samples. Furthermore, specimens overgrown by other bacteria using the culture method can be evaluated in the qPCR.

No aetiology is found in up to 40% of men with symptomatic urethritis. Male partners of women with bacterial vaginosis (BV) may be at higher risk of non-gonococcal urethritis (NGU). The aim of this study was to examine the role of BV associated bacteria in first-void urine (FVU) in 97 asymptomatic men without urethritis (controls) and 44 men (cases) with NGU including 20 men with idiopathic urethritis (IU) attending a Swedish STD-clinic between January and October 2010. BV-associated bacteria and ureaplasmas were detected by quantitative PCR assays. All BV associated bacteria, except Megasphaera -like type 1, were strongly positively correlated with U . urealyticum p<0.005 and even stronger with the combined U . urealyticum and U . parvum load (p<0.0005) suggesting that ureaplasma induced elevated pH may stimulate the growth of BV associated bacteria. No statistically significant differences were found between IU cases and controls in the prevalence or load of BV associated bacteria or ureaplasmas. In multiple logistic regression, Megasphaera -like type 1 was associated with IU (p = 0.03), but most positive FVU samples contained very few bacteria and the finding may not be clinically relevant.