Evaluation of the Bio-Rad Dx CT/NG/MG® assay for simultaneous detection of Chlamydia trachomatis, Neisseria gonorrhoeae and Mycoplasma genitalium in urine

Comparison of analytical sensitivity of DNA-based and RNA-based nucleic acid amplification tests for reproductive tract infection pathogens: implications for clinical applications

Currently, DNA-based nucleic acid amplification tests (NAATs) and RNA-based NAATs are employed to detect reproductive tract infection (RTI) pathogens including Chlamydia trachomatis (CT), Neisseria gonorrhoeae (NG), and Ureaplasma urealyticum (UU). Although evaluations of DNA-based NAATs have already existed, the comparison of the two methods is scarce. Thus, we compared the limits of detection (LODs) of DNA-based and RNA-based NAATs on the same experimental conditions. Inactivated culture supernatants of CT, NG, and UU with determined pathogen DNA and RNA load were used to evaluate LODs of seven DNA kits and one RNA kit. The LODs of the seven DNA kits for CT, NG, and UU ranged between 38-1,480, 94-20,011, and 132-2,011 copies/mL, respectively. As for RNA kits, they could detect samples at RNA concentrations of 3,116, 2,509, and 2,896 copies/mL, respectively. The RNA concentrations of CT, NG, and UU were 40, 885, and 42 times that of corresponding pathogen DNA concentrations in the employed supernatants, so RNA kits could detect pathogen DNA concentrations as low as 78 copies/mL, 3 copies/mL, and 69 copies/mL, respectively, but the level of pathogen load that the RNA tests could detect was primarily dependent on the infectious phase and transcriptional level of RNA. Thus, a schematic of bacterial dynamics during the period of reproductive tract infections was provided, which suggests that in terms of the analytical sensitivity of pathogen detection, RNA tests are more suitable for detecting active infection and recovery phase, while DNA tests are more suitable for detection in the early stage of infection. IMPORTANCE Reproductive tract infections have considerable effects on the health of humans. CT, NG , and UU are common pathogens. Although evaluation of DNA-based tests has already existed, the comparison between DNA-based and RNA-based tests is rare. Therefore, this study compared the limits of detection of the two tests on the same experimental conditions. Results suggested that most DNA-based NAATs could detect CT, NG, and UU at DNA concentrations lower than 1,000 copies/mL, while RNA-based NAATs could detect bacteria at RNA concentrations around 3,000 copies/mL. Considering the copy number of RNA per bacterium is dynamic through the growth cycle, further comparison is combined with a schematic of bacterial dynamics. Results suggested that in terms of the analytical sensitivity of pathogen detection, RNA tests are more suitable for detecting active infection and recovery phase, while DNA tests are more suitable for detection in the early stage of infection.

Latest Advances in Laboratory Detection of Mycoplasma genitalium

Mycoplasma genitalium is an important sexually transmitted pathogen affecting both men and women. Its extremely slow growth in vitro and very demanding culture requirements necessitate the use of molecular-based diagnostic tests for its detection in clinical specimens. The recent availability of U.S. Food and Drug Administration (FDA)-cleared commercial molecular-based assays has enabled diagnostic testing to become more widely available in the United States and no longer limited to specialized reference laboratories. Advances in the knowledge of the epidemiology and clinical significance of M. genitalium as a human pathogen made possible by the availability of molecular-based testing have led to updated guidelines for diagnostic testing and treatment that have been published in various countries. This review summarizes the importance of M. genitalium as an agent of human disease, explains the necessity of obtaining a microbiological diagnosis, describes currently available diagnostic methods, and discusses how the emergence of antimicrobial resistance has complicated treatment alternatives and influenced the development of diagnostic tests for resistance detection, with an emphasis on developments over the past few years.

AAUS guideline for chlamydial urethritis

Urogenital chlamydial infection is the most common sexually transmitted infection. Many cases of chlamydial infection are reported worldwide every year. Genital chlamydial infection in women can also cause obstetric issues, including infertility and miscarriage. For that purpose, appropriate care should be conducted with the latest knowledge. Only few guidelines come from Asian countries. The Asian Association of Urinary Tract Infection and Sexually Transmitted Infection (AAUS) belonging to the Urological Association of Asia (UAA) had developed the guidelines regarding chlamydial urethritis. We have collected the feedback and updated the guidelines which is now submitted for consideration of publication. In addition to the levels of evidence, the recommendation grades were defined using the modified GRADE methodology. Herein, we present the new edition of the UAA-AAUS guidelines for chlamydial urethritis.

A profile of the FDA-approved and CE/IVD-marked Aptima Mycoplasma genitalium assay (Hologic) and key priorities in the management of M. genitalium infections

INTRODUCTION

Mycoplasma genitalium (MG) causes frequently asymptomatic STIs. MG prevalence figures are lacking and management is complicated by the lack of etiological diagnostics and high antimicrobial resistance in many countries. Appropriately validated, quality-assured, and FDA-approved MG diagnostic assays have been lacking.

AREAS COVERED

The clinical and analytical performance characteristics of the Aptima® MG assay, the first FDA-approved MG nucleic acid amplification test (NAAT), are summarized. Key priorities in the management and control of MG infections are also discussed.

EXPERT OPINION

Highly sensitive, specific, and quality-assured MG NAATs, e.g. the Aptima MG assay on the automated and flexible Panther® platform, are imperative to improve the management and control of MG infections internationally. This testing, combined with macrolide-resistance testing (not yet available on the Panther platform), offers a rapid, high-throughput, and appropriate diagnosis of MG. Macrolide resistance-guided sequential treatment needs to be implemented for MG infections. Dual antimicrobial therapy, novel antimicrobials and, ideally, a vaccine may become essential.

The Laboratory Diagnosis of Neisseria gonorrhoeae: Current Testing and Future Demands

The ideal laboratory test to detect Neisseria gonorrhoeae (Ng) should be sensitive, specific, easy to use, rapid, and affordable and should provide information about susceptibility to antimicrobial drugs. Currently, such a test is not available and presumably will not be in the near future. Thus, diagnosis of gonococcal infections presently includes application of different techniques to address these requirements. Microscopy may produce rapid results but lacks sensitivity in many cases (except symptomatic urogenital infections in males). Highest sensitivity to detect Ng was shown for nucleic acid amplification technologies (NAATs), which, however, are less specific than culture. In addition, comprehensive analysis of antibiotic resistance is accomplished only by in vitro antimicrobial susceptibility testing of cultured isolates. As a light at the end of the tunnel, new developments of molecular techniques and microfluidic systems represent promising opportunities to design point-of-care tests for rapid detection of Ng with high sensitivity and specificity, and there is reason to hope that such tests may also provide antimicrobial resistance data in the future.

Comparison of rRNA-based and DNA-based nucleic acid amplifications for detection of Chlamydia trachomatis, Neisseria gonorrhoeae, and Ureaplasma urealyticum in urogenital swabs

Background

Nucleic acid amplification tests (NAAT) are well-accepted in diagnosis and surveillance of sexually infectious pathogens worldwide. However, performance differences between a RNA-based NAAT and DNA-based NAAT are rarely reported. This study compares the performances of the RNA-based SAT (simultaneous amplification and testing) assay and the DNA-based quantitative real-time polymerase chain reaction (qPCR) assay.

Methods

A total of 123 urogenital swabs were collected from outpatients with suspected genital infections in our hospital. Chlamydia trachomatis (CT), Neisseria gonorrhoeae (NG), and Ureaplasma urealyticum (UU) in these swabs were simultaneously tested by SAT and qPCR. Any swabs were positive in the qPCR assay were further verified by following cloning and sequencing. All statistical analysis was performed using the SPSS software.

Results

When the concentrations of CT, NG, or UU were more than 1 × 10³ copies/ml, 100% agreements between SAT and qPCR were observed regardless of the pathogen. No discrepancy was found. However, the sensitivity of SAT is significantly higher than qPCR in samples with concentration less than 1 × 10³ copies/ml. When tested by SAT and qPCR, 57.14 and 28.57% were positive for CT, 46.15% and 0 were positive for NG, 80% and 0 were positive for UU, respectively.

Conclusions

The SAT assay has better agreements and higher sensitivities when compared with the qPCR assay, and thus could be a better choice for screening, diagnosis, and surveillance of sexually transmitted diseases, especially for CT and NG.

Comparison between DiaPlexQ™ STI6 and GeneFinder™ STD I/STD II multiplex Real-time PCR Kits in the detection of six sexually transmitted disease pathogens

BACKGROUND

The DiaPlexQ™ STI6 Detection Kit (DiaPlexQ; Solgent Co., Ltd., Daejeon, South Korea) is a multiplex real-time PCR assay for the detection of the following sexually transmitted disease (STD) pathogens: Chlamydia trachomatis, Neisseria gonorrhoeae, Mycoplasma hominis, Trichomonas vaginalis, Ureaplasma urealyticum, and Mycoplasma genitalium. We compared the performance of the DiaPlexQ assay with the GeneFinder™ STD I (CT/NG/UU) and STD II (MG/MH/TV) Multiplex Real-time PCR Kits (GeneFinder; Infopia Co., Ltd., Anyang, South Korea).

METHODS

We evaluated the performance of the DiaPlexQ assay in comparison to that of GeneFinder using 1106 clinical specimens (542 genital swabs and 564 urine samples). The analytical performance of the DiaPlexQ assay, including the limit of detection (LOD) and analytical specificity, was evaluated using reference strains.

RESULTS

The positive percent agreement, negative percent agreement, and kappa value between the two assays were 96.6%-99.4%, 98.2%-99.8%, and 0.93%-0.99%, respectively. No cross-reactivity was observed in a collection of 41 different microorganisms and the LOD of the DiaPlexQ assay ranged from 1 to 10 copies/reaction for each microorganism.

CONCLUSION

The DiaPlexQ assay showed comparable performance to that of the GeneFinder assay so that it can be used for the screening and diagnosis of non-viral curable STD pathogens.

Prevalence of Mycoplasma genitalium in men with urethritis in a large public hospital in Brussels, Belgium: An observational, cross-sectional study

Background

Mycoplasma genitalium (MG) is a cause of urethritis. While resistance to azithromycin is increasing, routine detection of MG is not performed in Belgium, where its prevalence is unknown. The aim of this study is to determine prevalence of MG in men with urethritis.

Method and findings

An “in-house” amplification assay detecting MG was performed on urine of men with complaints of urethritis who consulted the emergency unit or the Sexually Transmitted Infection clinic of our public hospital in Brussels. Chlamydia trachomatis (CT) and Neisseria gonorrhoeae (NG) were tested on the same sample. A total of 187 men were tested. Prevalence of MG was 9% (95% Confidence Interval: 5 to 13.2%). CT was detected in 20%, NG in 22% and 56% of samples were negative for these three pathogens. Neither age, ethnic origin, sexual orientation nor HIV infection were associated with MG urethritis.

Conclusion

M. genitalium was identified in 9% of men with complaints of urethritis indicating that amplification assay detecting MG should be implemented in routine testing for those patients.

Should we screen for the sexually-transmitted infection Mycoplasma genitalium? Evidence synthesis using a transmission-dynamic model

There is increasing concern about Mycoplasma genitalium as a cause of urethritis, cervicitis, pelvic inflammatory disease (PID), infertility and ectopic pregnancy. Commercial nucleic acid amplification tests (NAATs) are becoming available, and their use in screening for M. genitalium has been advocated, but M. genitalium's natural history is poorly-understood, making screening's effectiveness unclear. We used a transmission-dynamic compartmental model to synthesise evidence from surveillance data and epidemiological and behavioural studies to better understand M. genitalium's natural history, and then examined the effects of implementing NAAT testing. Introducing NAAT testing initially increases diagnoses, by finding a larger proportion of infections; subsequently the diagnosis rate falls, due to reduced incidence. Testing only symptomatic patients finds relatively little infection in women, as a large proportion is asymptomatic. Testing both symptomatic and asymptomatic patients has a much larger impact and reduces cumulative PID incidence in women due to M. genitalium by 31.1% (95% range:13.0%-52.0%) over 20 years. However, there is important uncertainty in M. genitalium's natural history parameters, leading to uncertainty in the absolute reduction in PID and sequelae. Empirical work is required to improve understanding of key aspects of M. genitalium's natural history before it will be possible to determine the effectiveness of screening.

Should we screen for the sexually-transmitted infection Mycoplasma genitalium? Evidence synthesis using a transmission-dynamic model

There is increasing concern about Mycoplasma genitalium as a cause of urethritis, cervicitis, pelvic inflammatory disease (PID), infertility and ectopic pregnancy. Commercial nucleic acid amplification tests (NAATs) are becoming available, and their use in screening for M. genitalium has been advocated, but M. genitalium's natural history is poorly-understood, making screening's effectiveness unclear. We used a transmission-dynamic compartmental model to synthesise evidence from surveillance data and epidemiological and behavioural studies to better understand M. genitalium's natural history, and then examined the effects of implementing NAAT testing. Introducing NAAT testing initially increases diagnoses, by finding a larger proportion of infections; subsequently the diagnosis rate falls, due to reduced incidence. Testing only symptomatic patients finds relatively little infection in women, as a large proportion is asymptomatic. Testing both symptomatic and asymptomatic patients has a much larger impact and reduces cumulative PID incidence in women due to M. genitalium by 31.1% (95% range:13.0%-52.0%) over 20 years. However, there is important uncertainty in M. genitalium's natural history parameters, leading to uncertainty in the absolute reduction in PID and sequelae. Empirical work is required to improve understanding of key aspects of M. genitalium's natural history before it will be possible to determine the effectiveness of screening.