Simultaneous real-time PCR detection of nine prevalent sexually transmitted infections using a predesigned double-quenched TaqMan probe panel

Sexually transmitted diseases are major causes of infertility, ectopic pregnancy, and premature birth. Here, we developed a new multiplex real-time polymerase chain reaction (PCR) assay for the simultaneous detection of nine major sexually transmitted infections (STIs) found in Vietnamese women, including Chlamydia trachomatis, Neisseria gonorrhoeae, Gardnerella vaginalis, Trichomonas vaginalis, Candida albicans, Mycoplasma hominis, Mycoplasma genitalium, and human alphaherpesviruses 1 and 2. A panel containing three tubes × three pathogens/tube was predesigned based on double-quenched TaqMan probes to increase detection sensitivity. There was no cross-reactivity among the nine STIs and other non-targeted microorganisms. Depending on each pathogen, the agreement with commercial kits, sensitivity, specificity, repeatability and reproducibility coefficient of variation (CV), and limit of detection of the developed real-time PCR assay were 99.0%-100%, 92.9%-100%, 100%, <3%, and 8-58 copies/reaction, respectively. One assay cost only 2.34 USD. Application of the assay for the detection of the nine STIs in 535 vaginal swab samples collected from women in Vietnam yielded 532 positive cases (99.44%). Among the positive samples, 37.76% had one pathogen, with G. vaginalis (33.83%) as the most prevalent; 46.36% had two pathogens, with G. vaginalis + C. albicans as the most prevalent combination (38.13%); and 11.78%, 2.99%, and 0.56% had three, four, and five pathogens, respectively. In conclusion, the developed assay represents a sensitive and cost-effective molecular diagnostic tool for the detection of major STIs in Vietnam and is a model for the development of panel detections of common STIs in other countries.

Modelling-based evaluation of the costs, benefits and cost-effectiveness of multipathogen point-of-care tests for sexually transmitted infections in symptomatic genitourinary medicine clinic attendees

OBJECTIVES

To quantify the costs, benefits and cost-effectiveness of three multipathogen point-of-care (POC) testing strategies for detecting common sexually transmitted infections (STIs) compared with standard laboratory testing.

DESIGN

Modelling study.

SETTING

Genitourinary medicine (GUM) services in England.

POPULATION

A hypothetical cohort of 965 988 people, representing the annual number attending GUM services symptomatic of lower genitourinary tract infection.

INTERVENTIONS

The decision tree model considered costs and reimbursement to GUM services associated with diagnosing and managing STIs. Three strategies using hypothetical point-of-care tests (POCTs) were compared with standard care (SC) using laboratory-based testing. The strategies were: A) dual POCT for Chlamydia trachomatis (CT) and Neisseria gonorrhoeae (NG); B) triplex POCT for CT-NG and Mycoplasma genitalium (MG); C) quadruplex POCT for CT-NG-MG and Trichomonas vaginalis (TV). Data came from published literature and unpublished estimates.

PRIMARY AND SECONDARY OUTCOME MEASURES

Primary outcomes were total costs and benefits (quality-adjusted life years (QALYs)) for each strategy (2016 GB, £) and associated incremental cost-effectiveness ratios (ICERs) between each of the POC strategies and SC. Secondary outcomes were inappropriate treatment of STIs, onward STI transmission, pelvic inflammatory disease in women, time to cure and total attendances.

RESULTS

In the base-case analysis, POC strategy C, a quadruplex POCT, was the most cost-effective relative to the other strategies, with an ICER of £36 585 per QALY gained compared with SC when using microcosting, and cost-savings of £26 451 382 when using tariff costing. POC strategy C also generated the most benefits, with 240 467 fewer clinic attendances, 808 fewer onward STI transmissions and 235 135 averted inappropriate treatments compared with SC.

CONCLUSIONS

Many benefits can be achieved by using multipathogen POCTs to improve STI diagnosis and management. Further evidence is needed on the underlying prevalence of STIs and SC delivery in the UK to reduce uncertainty in economic analyses.

Sexually transmitted rectal infections in a cohort of 'men having sex with men'

PURPOSE

We assessed the prevalence and predictors of Chlamydia trachomatis, Neisseriagonorrhoeae and Mycoplasmagenitalium rectal infections in a population of 'men having sex with men' (MSM).

METHODOLOGY

From January to November 2017, 165 MSM attending a STI outpatients clinic in Bologna (Italy) and reporting unsafe anal intercourses were enrolled. An ano-rectal swab was collected from each patient: chlamydial and gonococcal infections were diagnosed by a commercial NAAT, whereas an in-house quantitative PCR was used for M. genitalium detection. In addition, 131 urine samples and 84 pharyngeal swabs underwent testing for C. trachomatis and N. gonorrhoeae. A molecular C. trachomatis typing, a serological screening for anti-Chlamydia IgG and IgA, as well as the assessment of HIV, HCV and syphilis infections, were performed.Results/Key findings. The prevalence of C. trachomatis, N. gonorrhoeae and M. genitalium rectal infections was 27.2, 25.4 and 4.8 %, respectively. Globally, 63.1 % of cases were asymptomatic and up to 80 % of chlamydial and gonococcal infections would have been missed if the rectal site had not been tested. All the patients with rectal M. genitalium carriage were asymptomatic and characterized by low bacterial loads (<2500 DNA copies/reaction). Lymphogranuloma venereum (LGV) prevalence was 12.1 % with a considerable proportion of asymptomatic infections (35 %). The presence of symptoms, age >30, HIV-positivity and elevated levels of anti-Chlamydia antibodies were the most significant predictors of LGV.

CONCLUSIONS

Sexually transmitted rectal infections are frequent and often asymptomatic among MSM. LGV prevalence is high in our country and there is increasing evidence of symptomless cases.

Gardnerella vaginalis and Mollicute detection in rectal swabs from men who have sex with men

The numbers of rectal sexually transmitted infections are on the rise especially among men who have sex with men. Males from men who have sex with men population are encouraged to send a rectal swab to the laboratory for sexually transmitted infection screening at their visit to the Genitourinary Medicine Clinic. In healthy asymptomatic males, the range of pathogens tested is limited therefore other pathogens may be left untreated allowing infections to persist among sexual partners. Molecular techniques have revolutionarised sexually transmitted infection testing enabling the detection of previously difficult-to-culture pathogens in extra-genital sites and have increased the evidence base for their clinical significance. The present study tests 107 rectal swabs from men who have sex with men negative for Chlamydia trachomatis and Neisseria gonorrhoeae against quantitative polymerase chain reaction (qPCR) assays targeting five common sexually transmitted bacteria which include Mycoplasma genitalium, Mycoplasma hominis, Ureaplasma urealyticum, Ureaplasma parvum and Gardnerella vaginalis. The pathogenic role of these five bacteria in men who have sex with men is currently unknown. Amongst the 107 patients, a positive qPCR was obtained respectively for G. vaginalis 89 (83.2%); U. urealyticum 26 (24.3%); M. hominis 26 (24.3%); M. genitalium 10 (9.3%) and U. parvum 5 (4.7%). Bacterial loads in single and co-infections were compared for each organism. G. vaginalis and M. hominis loads were significantly ( p = 0.007 and p = 0.005, respectively) higher when co-infecting with at least one other organism. Amongst co-infections, the loads of each organism were assessed to determine possible synergies. G. vaginalis and M. hominis displayed a synergistic pattern ( r = 0.51; p = 0.02) which is in keeping with a similar synergy detected previously in the vagina of women with bacterial vaginosis. This study outlines that potential significant infections are being missed in men who have sex with men population; however, further research is warranted to confirm a pathogenesis in the rectal mucosa before routine screening can be introduced to clinical settings.

Evaluation of the Hologic Panther Transcription-Mediated Amplification Assay for Detection of Mycoplasma genitalium

The detection of Mycoplasma genitalium was evaluated on 1,080 urine samples by the use of a Panther instrument. Overall sensitivity, specificity, positive predictive values, and negative predictive values were 100%, 99.4%, 93.6%, and 100%, respectively. Detection of M. genitalium by the use of the Panther transcription-mediated amplification assay offers a simple, accurate, and sensitive platform for diagnostic laboratories.

The common vaginal commensal bacterium Ureaplasma parvum is associated with chorioamnionitis in extreme preterm labor

OBJECTIVE

To assess the association of vaginal commensal and low-grade pathogenic bacteria including Ureaplasma parvum, Ureaplasma urealyticum, Mycoplasma hominis, Mycoplasma genitalium, Group B streptococcus (GBS), and Gardnerella vaginalis, in women who delivered preterm at less than 37-week gestation in the presence or absence of inflammation of the chorioamnionitic membranes.

METHODS

A case control study involving women who delivered before 37-week gestation with and without inflammation of chorioamnionitic membranes. A total of 57 placental samples were histologically examined for polymorphonuclear leukocyte infiltration of placental tissue for evidence of chorioamnionitis, and by type-specific nucleic acid amplification for evidence of infection with one or more of the target bacteria. Demographic data were collected for each mother.

RESULTS

Among the 57 placental samples, 42.1% had chorioamnionitis and 24.6% delivered in the second trimester of pregnancy; U. parvum, U. urealyticum, G. vaginalis, and GBS were all detected in the study with respective prevalence of 19.3%, 3.5%, 17.5%, and 15.8%; M. genitalium and M. hominis were not detected. U. parvum was significantly associated with chorioamnionitis (p = 0.02; OR 5.0; (95% CI 1.2-21.5) and was more common in women who delivered in the second (35.7%) compared to the third trimester of pregnancy (13.9%). None of the other bacteria were associated with chorioamnionitis or earlier delivery, and all G. vaginalis-positive women delivered in the third trimester of pregnancy (p = 0.04).

CONCLUSIONS

The detection of U. parvum in placental tissue was significantly associated with acute chorioamnionitis in women presenting in extreme preterm labor.

Mycoplasma hominis and Gardnerella vaginalis display a significant synergistic relationship in bacterial vaginosis

Gardnerella vaginalis plays an important role in bacterial vaginosis (BV,) while the role of genital Mollicutes is less obvious. The diagnosis of BV by use of the current Gram stain Nugent score is also suboptimal for defining the role of Mollicutes that lack a cell wall. Since bacterial load and diversity is an important prerequisite for BV, real-time quantitative polymerase chain reaction (qPCR) assays enable these to be assessed. The purpose of this study was to define the role of genital Mollicutes and potential patterns of synergy with G. vaginalis in women with BV. Vaginal swabs from 130 women categorised by Nugent score as BV (n = 28), intermediate (n = 22) and non-BV (n = 80) were tested against four qPCR TaqMan assays targeting G. vaginalis, Mycoplasma hominis, M. genitalium, Ureaplasma urealyticum and U. parvum. Statistical analyses were used to compare bacterial prevalence and load between the three groups of women. Mycoplasma hominis and G. vaginalis co-infection was significantly more common in BV (60.7 %) compared to intermediate (36.4 %) and non-BV (8.8 %) Nugent scores (p < 0.001). Significantly higher loads of M. hominis (p = 0.001) and G. vaginalis (p < 0.001) were detected in women with BV and the respective loads in M. hominis and G. vaginalis co-infections displayed a significant positive correlation (p < 0.001; r = 0.60). No significant associations were seen with the other Mollicutes. The findings strengthen the evidence of a role for M. hominis in BV and a potential synergy with G. vaginalis. This synergy could be an important trigger of the condition and sexual contact the conduit for the transmission of an otherwise commensal bacterium that could initiate it.

Ureaplasma parvum and Mycoplasma genitalium are found to be significantly associated with microscopy-confirmed urethritis in a routine genitourinary medicine setting

Inflammation of the urethra defined by an excess of polymorphonuclear leukocytes in the absence of sexually transmitted Chlamydia trachomatis and Neisseria gonorrhoeae is called non-chlamydial non-gonococcal urethritis (NCNGU). Although Mycoplasma genitalium is now recognised as causing a sexually transmitted infection, the clinical significance of the other Mollicute species is less clear. This study used specific real-time quantitative polymerase chain reaction assays to detect and quantify four Mollicute species, M. genitalium, M. hominis, Ureaplasma urealyticum and U. parvum, in urine specimens from men with and without NCNGU. A total of 165 urine specimens from male patients attending a genitourinary medicine clinic were eligible for the study, with microscopy-confirmed (≥5 polymorphonuclear leukocytes in urethral swab) NCNGU in 75 (45.5%) and non-confirmed NCNGU in 90 (54.5%). Chi-squared statistical analysis indicated a significantly higher prevalence of U. parvum (17.3% vs. 5.6%; p = 0.03) and M. genitalium (12% vs. 0%; p < 0.001) in NCNGU. In a subset analysis, M. genitalium was also significantly (p = 0.03) higher in men who have sex with men (MSM; 13.5%) compared to non-MSM (3.1%). No significant associations were reported for U. urealyticum and M. hominis In conclusion, this study supports a clinically significant role in NGNCU for both U. parvum and M. genitalium.

Mycoplasma genitalium: a review

Mycoplasma genitalium (M. genitalium) was first isolated from the urethral swabs of two symptomatic men with urethritis in 1980. Published prevalence rates vary greatly between populations studied. A number of urogenital conditions have been ascribed to M. genitalium, which is recognised to cause a sexually transmitted infection. The association of M. genitalium with non-specific urethritis is now well established, but the evidence supporting its role in both male and female infertility remains inconclusive. Laboratory methods are challenging and there is a lack of test standardisation. The recommended treatment of the infection is azithromycin as a single 1 gm dose. However, in recent years macrolide resistance has been observed. More studies are required to establish the clinical importance of M. genitalium in urogenital conditions, particularly infertility, and to establish the role for screening and treatment in high-risk populations.

A cross-sectional study of Mycoplasma genitalium infection and correlates in women undergoing population-based screening or clinic-based testing for Chlamydia infection in London

OBJECTIVE

To determine Mycoplasma genitalium infection and correlates among young women undergoing population-based screening or clinic-based testing for Chlamydia infection.

DESIGN

Cross-sectional study.

SETTING

National Chlamydia Screening Programme (NCSP) and two London sexually transmitted infection (STI) clinics.

PARTICIPANTS

2441 women aged 15-64 years who participated in the NCSP and 2172 women who attended two London STI clinics over a 4-month period in 2009.

OUTCOME MEASURES

(1) M genitalium prevalence in defined populations (%). (2) Age-adjusted ORs (aORs) for correlates of M genitalium infection.

RESULTS

The overall frequency of M genitalium and Chlamydia trachomatis was 3% and 5.4%, respectively. Co-infection was relatively uncommon (0.5% of all women); however 9% of women with C trachomatis also had M genitalium infection. M genitalium was more frequently detected in swab than urine samples (3.9 vs 1.3%, p<0.001) with a significantly higher mean bacterial load (p ≤ 0.001). Among NCSP participants, M genitalium was significantly more likely to be diagnosed in women of black/black British ethnicity (aOR 2.3, 95% CI 1.2 to 4.5, p=0.01). M genitalium and C trachomatis and were both significantly associated with multiple sexual partners in the past year (aOR 2.4, 95% CI 1.3 to 4.4, p=0.01 and aOR 2.0, 95% CI 1.4 to 2.8, p<0.01). Among STI clinic attendees, M genitalium was more common in women who were less than 25 years in age.

CONCLUSIONS

M genitalium is a relatively common infection among young women in London. It is significantly more likely to be detected in vulvovaginal swabs than in urine samples. Co-infection with Chlamydia is uncommon. The clinical effectiveness of testing and treatment strategies for M genitalium needs further investigation.

Real-time PCR as a diagnostic tool for bacterial diseases

In recent years, quantitative real-time PCR tests have been extensively developed in clinical microbiology laboratories for routine diagnosis of infectious diseases, particularly bacterial diseases. This molecular tool is well-suited for the rapid detection of bacteria directly in clinical specimens, allowing early, sensitive and specific laboratory confirmation of related diseases. It is particularly suitable for the diagnosis of infections caused by fastidious growth species, and the number of these pathogens has increased recently. This method also allows a rapid assessment of the presence of antibiotic resistance genes or gene mutations. Although this genetic approach is not always predictive of phenotypic resistances, in specific situations it may help to optimize the therapeutic management of patients. Finally, an approach combining the detection of pathogens, their mechanisms of antibiotic resistance, their virulence factors and bacterial load in clinical samples could lead to profound changes in the care of these infected patients.

Recent perspectives in the diagnosis and evidence-based treatment of Mycoplasma genitalium

Mycoplasma genitalium is a globally important sexually transmitted pathogen. Men infected with M. genitalium frequently present with dysuria, while women may present with or without urogenital symptoms. In some populations, M. genitalium is significantly associated with HIV-1 infection, and is also an etiological agent in pelvic inflammatory disease. However, there is insufficient evidence to establish a causative role of the organism in obstetric complications, including tubal factor infertility. Although several nucleic acid amplification tests offer rapid, sensitive methods for detecting M. genitalium, there is no standardized assay. Available evidence supports treatment of M. genitalium infections with an extended regimen of azithromycin and resistant strains respond to moxifloxacin. Accumulating evidence indicates growing fluoroquinolone resistance, including against moxifloxacin, emphasizing the need for new therapeutic strategies to treat M. genitalium infections.

Mycoplasma genitalium: from Chrysalis to multicolored butterfly

The history, replication, genetics, characteristics (both biological and physical), and factors involved in the pathogenesis of Mycoplasma genitalium are presented. The latter factors include adhesion, the influence of hormones, motility, possible toxin production, and immunological responses. The preferred site of colonization, together with current detection procedures, mainly by PCR technology, is discussed. The relationships between M. genitalium and various diseases are highlighted. These diseases include acute and chronic nongonococcal urethritis, balanoposthitis, chronic prostatitis, and acute epididymitis in men and urethritis, bacterial vaginosis, vaginitis, cervicitis, pelvic inflammatory disease, and reproductive disease in women. A causative relationship, or otherwise strong association, between several of these diseases and M. genitalium is apparent, and the extent of this, on a subjective basis, is presented; also provided is a comparison between M. genitalium and two other genital tract-orientated mollicutes, namely, Mycoplasma hominis, the first mycoplasma of human origin to be discovered, and Ureaplasma species. Also discussed is the relationship between M. genitalium and infertility and also arthritis in both men and women, as is infection in homosexual and immunodeficient patients. Decreased immunity, as in HIV infections, may enhance mycoplasmal detection and increase disease severity. Finally, aspects of the antimicrobial susceptibility and resistance of M. genitalium, together with the treatment and possible prevention of mycoplasmal disease, are discussed.

A review of the epidemiology, diagnosis and evidence-based management of Mycoplasma genitalium

Mycoplasma genitalium is attracting increasing recognition as an important sexually transmitted pathogen. Presented is a review of the epidemiology, detection, presentation and management of M. genitalium infection. Accumulating evidence suggests that M. genitalium is an important cause of non-gonococcal, non-chlamydial urethritis and cervicitis, and is linked with pelvic inflammatory disease and, possibly, obstetric complications. Although there is no standard detection assay, several nucleic acid amplification tests have >95% sensitivity and specificity for M. genitalium. To date, there is a general lack of established protocols for screening in public health clinics. Patients with urethritis or cervicitis should be screened for M. genitalium and some asymptomatic sub-groups should be screened depending on individual factors and local prevalence. Investigations estimating M. genitalium geographic prevalence document generally low incidence, but some communities exhibit infection frequencies comparable to that of Chlamydia trachomatis. Accumulating evidence supports an extended regimen of azithromycin for treatment of M. genitalium infection, as data suggest that stat 1 g azithromycin may be less effective. Although data are limited, azithromycin-resistant cases documented to date respond to an appropriate fluoroquinolone (e.g. moxifloxacin). Inconsistent clinical recognition of M. genitalium may result in treatment failure and subsequent persistence due to ineffective antibiotics. The contrasting nature of existing literature regarding risks of M. genitalium infection emphasises the need for further carefully controlled studies of this emerging pathogen.

Comparison of two Mycoplasma genitalium real-time PCR detection methodologies

Established in-house quantitative PCR (qPCR) assays to detect the Mycoplasma genitalium adhesion protein (MgPa) and the 16S rRNA gene were found to be comparable for screening purposes, with a kappa value of 0.97 (95% confidence interval [CI], 0.94 to 1.01) and no difference in bacterial load quantified (P = 0.4399).