Evaluation of the ResistancePlus MG FleXible Assay for Detection of Wild-Type and 23S rRNA-Mutated Mycoplasma genitalium Strains

2023 Korean sexually transmitted infections treatment guidelines for Mycoplasma genitalium by KAUTII

The Korean Association of Urogenital Tract Infection and Inflammation and the Korea Disease Control and Prevention Agency updated the Korean sexually transmitted infections (STIs) guidelines to respond to the changing epidemiologic trends, evolving scientific evidence, and advances in laboratory diagnostics and research. The main recommendations in the Mycoplasma genitalium infection parts of the Korean STIs guidelines 2023 revision are as follows: 1) For initial treatment: azithromycin 500 mg orally in a single dose, then 250 mg once daily for 4 days. 2) In case of treatment failure or recurrence, a macrolide susceptibility/resistance test is required, when susceptibility/resistance test is not feasible, doxycycline or minocycline 100 mg orally twice daily for 7 days, followed by azithromycin 1 g orally on the first day, then azithromycin 500 mg orally once daily for 3 days and then a test-of-cure should be considered 3 weeks after completion of therapy. 3) In case of macrolide sensitivity, doxycycline or minocycline 100 mg orally twice daily for 7 days, followed by azithromycin 1 g orally initial dose, then azithromycin 500 mg orally once daily for 3 days. 4) In case of macrolide resistance, doxycycline or minocycline 100 mg orally twice daily for 7 days, followed by moxifloxacin 400 mg orally once daily for 7 days. In the Korean STIs guideline 2023, macrolide resistance-guided antimicrobial therapy was emphasized due to the increased prevalence of macrolide resistance worldwide. Therefore, in case of treatment failure or recurrence, a macrolide susceptibility/resistance test is required.

Comparative analysis of five etiological detecting techniques for the positive rates in the diagnosis of tuberculous granuloma

Purpose

To examine the relationship between the positive rate and types of necrosis in pathological examinations of tuberculosis granulomas with necrosis, to improve the detection rate of positive cases.

Methods

Specimens from 381 patients were collected in Wuhan Pulmonary Hospital from Jan 2022 to Feb 2023. The samples were examined using various methods such as AFB smear microscopy, mycobacterial culture, PCR, SAT-TB, and X-pert MTB/RIF rapid molecular detection.

Result

There were 3 types of necrosis. Including 270 cases of caseous necrosis, 30 cases of coagulation necrosis, and 76 cases of an abscess. Five cases were non-necrotizing granulomas.In the pathological specimen testing for tuberculosis, five detection techniques were used and their positive rates detected in descending order were X-pert, TBDNA, SAT-TB, tuberculosis culture, AFB. Comparison between different examinations in the group: X-pert had the highest positive rate in each group, and it was significantly higher than TBDNA (P < 0.01) in caseous necrosis specimens. Compared with the same examination between the groups, the detection rates of X-pert and TBDNA in abscess and caseous necrosis specimens were significantly higher than in coagulation necrosis specimens (P < 0.01).

Conclusion

The positive rates of the five etiological detection techniques in tuberculous granuloma with different types of necrosis were quite different. The specimens of caseous necrosis or abscess could be selected for detection, and X-pert had the highest positive rate.

Point-of-Care Amenable Detection of Mycoplasma genitalium and Its Antibiotic Resistance Mutations

Mycoplasma genitalium (MG) is an emerging sexually transmitted bacterium. Due to its fastidious and slow-growing nature, MG is difficult to detect through culture-based diagnostics. Like Neisseria gonorrheae, another bacterial pathogen linked to sexually transmitted infections (STIs), MG has developed resistance to macrolide and fluoroquinolone antibiotics used to treat STIs. The ability to detect MG and identify genomic mutations associated with antibiotic resistance simultaneously can enable antibiotic stewardship and mitigate the spread of antibiotic-resistant MG. Toward this end, we first developed a multiplexed probe-based PCR-melt assay that detects MG and the presence of macrolide resistance mutations in the 23S rRNA gene and fluoroquinolone resistance mutations in the parC gene. Each target was identified via its unique combination of fluorescence label and melting temperature. This approach allowed differentiation between the different types of mutations at the genes of interest. Following initial assay optimization, the assay was integrated into a droplet magnetofluidic cartridge used in a portable platform to integrate automated sample extraction, PCR amplification, and detection. Lastly, we demonstrated that the integrated assay and droplet magnetofluidic platform could detect MG and antibiotic resistance-associated mutations in clinical isolates spiked into urine samples in 40 min.

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.

Bridging the gap between development of point-of-care nucleic acid testing and patient care for sexually transmitted infections

The incidence rates of sexually transmitted infections (STIs), including the four major curable STIs - chlamydia, gonorrhea, trichomoniasis and, syphilis - continue to increase globally, causing medical cost burden and morbidity especially in low and middle-income countries (LMIC). There have seen significant advances in diagnostic testing, but commercial antigen-based point-of-care tests (POCTs) are often insufficiently sensitive and specific, while near-point-of-care (POC) instruments that can perform sensitive and specific nucleic acid amplification tests (NAATs) are technically complex and expensive, especially for LMIC. Thus, there remains a critical need for NAAT-based STI POCTs that can improve diagnosis and curb the ongoing epidemic. Unfortunately, the development of such POCTs has been challenging due to the gap between researchers developing new technologies and healthcare providers using these technologies. This review aims to bridge this gap. We first present a short introduction of the four major STIs, followed by a discussion on the current landscape of commercial near-POC instruments for the detection of these STIs. We present relevant research toward addressing the gaps in developing NAAT-based STI POCT technologies and supplement this discussion with technologies for HIV and other infectious diseases, which may be adapted for STIs. Additionally, as case studies, we highlight the developmental trajectory of two different POCT technologies, including one approved by the United States Food and Drug Administration (FDA). Finally, we offer our perspectives on future development of NAAT-based STI POCT technologies.

Performance of Three Commercial Molecular Diagnostic Assays for the Simultaneous Detection of Mycoplasma genitalium and Macrolide Resistance

The increasing frequency of macrolide resistance is an emerging issue in the treatment of Mycoplasma genitalium infection. Because evaluation of new commercial kits detecting M. genitalium and macrolide resistance is needed, we evaluated the performance and handling characteristics of the Allplex MG & AziR (Seegene), the Macrolide-R/MG ELITe MGB (ELITechGroup), and the ResistancePlus MG FleXible (SpeeDx-Cepheid) kits in comparison with those of an in-house real-time PCR and 23S rRNA gene sequencing used as the reference. A total of 239 urogenital specimens (135 M. genitalium-positive and 104 M. genitalium-negative specimens) collected between April and December 2019 at the French National Reference Center for Bacterial Sexually Transmitted Infections were assessed. The overall agreement for M. genitalium detection of the three commercial kits compared with the in-house real-time PCR was 94.6 to 97.6%, and there was no significant difference. A total of 97 specimens were found to be M. genitalium positive with the three kits and were used to assess macrolide resistance detection. The clinical sensitivities for resistance detection were 74.5% (95% confidence interval, 61.7 to 84.2%), 96.2% (87.2 to 99.0%), and 92.8% (82.7 to 97.1%) for the Allplex MG & AziR, Macrolide-R/MG ELITe MGB, and ResistancePlus MG FleXible kits, respectively. The sensitivity of the Macrolide-R/MG ELITe MGB kit was significantly higher than that of the Allplex MG & AziR kit. The clinical specificity for resistance detection of the three kits was 97.4 to 97.6%. The random-access possibility, input sample volume, and DNA extract availability for detecting resistance to other antibiotics may also influence the selection of a commercial kit by diagnostic laboratories.

The Impact of Selected Bacterial Sexually Transmitted Diseases on Pregnancy and Female Fertility

Sexually transmitted infections (STIs) caused by Neisseria gonorrhoeae, Chlamydia trachomatis and Mycoplasma genitalium are a common cause of pelvic inflammatory disease (PID) which can lead to tubal factor infertility (TFI). TFI is one of the most common causes of infertility, accounting for 30% of female fertility problems. STIs can also have an impact on pregnancy, leading to adverse pregnancy outcomes. Escalating antibiotic resistance in Neisseria gonorrhoeae and Mycoplasma genitalium represents a significant problem and can be therapeutically challenging. We present a comprehensive review of the current treatment options, as well as the molecular approach to this subject. We have given special attention to molecular epidemiology, molecular diagnostics, current and new treatments, and drug resistance.

Comparison of three real-time PCR methods for detection of macrolide-resistant Mycoplasma genitalium in Sweden

There is a worldwide increase in macrolide-resistant Mycoplasma genitalium strains, with severe impacts on treatment. The aim of this study was to compare three real-time PCR methods for the detection of macrolide resistance: an in-house PCR described by Touati et al., ResistancePlus® MG (SpeeDx), and S-DiaMGRes™ (Diagenode Diagnostics). One hundred M. genitalium-positive patient samples collected in Sweden and a quantitated M. genitalium DNA control were analyzed. Macrolide resistance was detected in 18, 15, and 16 of the samples with the respective methods. Sequencing of the 23S rRNA gene confirmed resistance in 16 (16%) of 100 samples in which it was detected with any of the three methods. ResistancePlus® MG and S-DiaMGRes™ falsely determined one sample as macrolide-sensitive, but this sample was determined as resistant when retested. The sensitivity of the methods was comparable, although there should be awareness of possible incorrect determination of macrolide resistance, especially of low-positive samples.

Evaluation of ResistancePlus MG FleXible, a 'near-patient' test for the detection of Mycoplasma genitalium and macrolide resistance mutations, using freshly collected clinical samples

Introduction. Mycoplasma genitalium is a sexually transmitted pathogen with increasing resistance to first- and second-line antimicrobials. The 'near-patient test' ResistancePlus MG FleXible (SpeeDx) detects M. genitalium plus four macrolide resistance mutations (MRMs), facilitating same-day patient follow up.Hypothesis/Gap Statement. This assay has not been assessed on freshly collected samples.Aim. Our goal was to evaluate the performance of the ResistancePlus MG FleXible test against the standard of care open platform test.Methods. ResistancePlus MG FleXible (analysed on the Cepheid GeneXpert platform) was evaluated on freshly collected samples and compared to the standard of care open platform test ResistancePlus MG (SpeeDx) analysed on the LightCycler 480 II (Roche).Results. For 270 valid tests, ResistancePlus MG FleXible yielded a high positive per cent agreement (PPA) of 94.1% [96/102; 95 % confidence interval (CI): 87.6-97.8 %] and negative per cent agreement (NPA) of 95.2% (160/168; 95 % CI: 90.8-97.9%) for M. genitalium detection compared to the reference assay (kappa for test concordance of 0.89; 95 % CI: 0.83-0.95). Performance was similar across different sample types. For the detection of MRMs, ResistancePlus MG FleXible had a PPA of 97.1% (66/68; 95% CI: 89.8-99.6) and NPA of 78.6% (22/28; 95 % CI: 59.0-91.7), with test comparison kappa of 0.79 (95 % CI: 0.65-0.93). Notably, of six discordant results (i.e. determined to be wild type by the reference assay), five were positive for MRMs by Sanger sequencing, indicating that the ResistancePlus MG FleXible assay has an improved performance for mutation detection.Conclusion. ResistancePlus MG FleXible had comparable test performance for M. genitalium detection as the open platform assay, with improved detection of MRMs. The ResistancePlus MG FleXible 'near-patient' assay can deliver a rapid result to expedite appropriate treatment.

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.

Point-by-Point Progress: Gonorrhea Point of Care Tests

INTRODUCTION

Point-of-care (POC) tests for Neisseria gonorrhoeae (Ng) are urgently needed to control the gonorrhea epidemic, so patients can receive immediate diagnoses and treatment. While the advent of nucleic acid amplification tests (NAATs) has improved the accuracy of Ng identification, very few POC assays are able to provide results of such tests at the clinical visit. Additionally, antimicrobial resistance (AMR) presents a unique treatment challenge for Ng.

AREAS COVERED

This review notes that older POC tests have lower sensitivity for Ng, compared to the currently-available NAATs, and are not adequate for the current demand for high sensitivity. Promising newer assays, which can be used at the POC are covered. This review also includes data about clinicians' and patients' acceptability and expectations of POC tests for Ng, testing of extragenital specimens, pooling studies, as well as their impact clinically, and use in low-resource settings.

EXPERT OPINION

The ability to use POC tests to identify and immediately treat Ng infections at the patient encounter offers many benefits and opportunities. POC tests for Ng are currently available, but not widely used especially in low-resource settings. Further development of POC tests with AMR testing capacity is needed to help guide antimicrobial stewardship.