Sensitive and specific assay for the simultaneous detection of Mycoplasma genitalium and macrolide resistance-associated mutations

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.

Azithromycin treatment failure and macrolide resistance in Mycoplasma genitalium infections in Sofia, Bulgaria

INTRODUCTION

Mycoplasmagenitalium is an established cause of sexually transmitted infections in men and women. Current guidelines recommend azithromycin and moxifloxacin as first- and second-line treatment, respectively. However, azithromycin treatment failure has been increasingly reported. The aim of this study was to determine the efficacy of azithromycin and alternative antibiotic regimens in a prospective cohort of M.genitalium-positive patients, and macrolide resistance mutations associated with azithromycin failure.

Molecular epidemiology and antimicrobials resistance mechanism of Mycoplasma genitlaium

Currently, infections caused by Mycoplasma genitalium are ones the most common sexually transmitted infections. Their prevalence is varied from 1.3% to 15.9%. Infections caused by M.genitalium may lead to urethritis in men and a wide spectrum of diseases in women. Antibiotic resistance now is one of the most emerging problems both in the scientific and in the healthcare fields. The usage of antimicrobials inhibiting cell wall synthesis for the treatment of M.genitalium is ineffective, and resistance to macrolides and fluoroquinolones is increasing rapidly. M.genitalium infections diagnostics is complicated due to specific conditions and duration of culture methods. The usage of nucleic acid amplification techniques is the most relevant for laboratory diagnostics, and is used in existing assays. This review compiles current data on the prevalence, molecular mechanisms of pathogenesis and antibiotic resistance, as well as diagnostics methods of M.genitalium.

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.

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.

Evaluating the prevalence and risk factors for macrolide resistance in Mycoplasma genitalium using a newly developed qPCR assay

Mycoplasma genitalium (MG) is a sexually transmitted bacterium in which macrolide resistance is rapidly increasing, limiting treatment options. We validated a new assay to detect the presence of macrolide resistance-associated mutations in MG (MG-MRAM). In 2018, symptomatic and asymptomatic clients visiting sexually transmitted infections (STI) clinics in Amsterdam or The Hague were tested for MG using transcription mediated amplification (TMA) assays. The sensitivity to detect MG of the newly developed MG-MRAM qPCR was compared to the MgPa qPCR, both in relation to the TMA assay. For the sensitivity and specificity to detect relevant mutations the MG-MRAM qPCR was compared to 23SrRNA sequencing analysis. The qPCR was subsequently used to determine the presence of MG-MRAM at different anatomical locations and to identify risk factors for MG-MRAM. MG-positive clients (402) providing 493 MG-positive samples were included. In total 309/493 (62.7%) samples from 291 (72.4%) clients were successfully typed with the MG-MRAM qPCR. The MG-MRAM qPCR had a sensitivity of 98.6% (95%CI 91.1%-99.9%) and specificity of 94.1% (95%CI 78.9%-99.0%) to detect MG-MRAM compared to sequencing analysis. Infection with MG-MRAM was detected in 193/291 (66.3%) clients: in 129/178 (72.5%) men and 64/113 (56.6%) women (p = 0.005). Prevalence of MG-MRAM was significantly higher in men, clients with a higher education, HIV-positive clients and clients with >10 sexual partners in the previous six months, but in multivariable analysis no factor was significantly associated with MG-MRAM presence. Since MG-MRAM prevalence was very high, testing for MG-MRAM is essential if treatment for MG is considered, and can be performed with this sensitive and specific qPCR test in routine diagnostics.

Mycoplasma genitalium and antimicrobial resistance in Europe: a comprehensive review

Antibiotic resistance in Mycoplasma genitalium has been emerging in Europe. Also, discrepancies on the management and treatment of sexually transmitted infections may have distinctly influenced the prevalence of antimicrobial resistance among European countries. This comprehensive review of the literature published between 2012 and 2018 updates antimicrobial resistance data in M. genitalium in Europe. Overall, macrolide resistance is rapidly increasing in this region, where many countries are exceeding 50%. The limited data regarding fluoroquinolone resistance estimate a prevalence of 5% (interquartile range, 5–6%). The study supports the need to conduct representative and well-defined surveillance on antimicrobial resistance in M. genitalium at both local and European levels. Also, further investigations on new promising antibiotics are required to fight against M. genitalium that may soon become untreatable.

Molecular basis of antimicrobial resistance in Mycoplasma genitalium

Mycoplasma genitalium is a sexually transmitted urogenital pathogen, and infection can result in serious symptoms. As M. genitalium is rather difficult to culture, infections are usually detected by molecular methods. Unfortunately, there has recently been a significant increase in resistance to azithromycin and moxifloxacin used for the treatment of M. genitalium infections. The increased resistance to (often empirically prescribed) M. genitalium treatments has resulted in frequent therapy failures and stresses the need for routine detection of antimicrobial resistance. In M. genitalium, antimicrobial resistance is almost always the result of DNA mutations and thus can easily be detected by molecular techniques. Regrettably, many microbiology laboratories do not use molecular techniques for the detection of bacterial antimicrobial resistance. As molecular tests are becoming available for M. genitalium, both for the establishment of infection and the detection of antimicrobial resistance, it is now more important to ensure that knowledge on the resistance mechanisms is transferred from the laboratory to the clinician. This review will provide a brief summary of the current status of antimicrobial resistance, its molecular mechanisms and the impact on the current status of M. genitalium treatment.

A profile of the cobas® TV/ MG test for the detection of Trichomonas vaginalis and Mycoplasma genitalium

Introduction: Trichomonas vaginalis and Mycoplasma genitalium are highly prevalent sexually transmitted pathogens that may be asymptomatic or may cause cervicitis and pelvic inflammatory disease in women and urethritis in men. Our limited understanding of the epidemiology of these infections has been hampered by a lack of diagnostic capacity, but the new cobas® TV/MG assay runs on the cobas® 6800/8800 platform offers a solution to this gap in our current diagnostic capacity.Areas covered: This article will describe what we know about the epidemiology and impact of untreated infections with these organisms as well as current recommendations for testing. The features and performance of the cobas 6800/8800 and the TV/MG assay will be described based on the emerging data related to this assay.Expert commentary: Molecular diagnostics for trichomonas and mycoplasma that can be performed on a high-throughput system with the flexibility to order only those tests required are needed in order to reduce the burden of disease and of consequences of undiagnosed infections caused by these pathogens. As a result of the complexities in the needs for testing in different populations, sample-specific flexibility in test ordering is an absolute need in the molecular laboratory.

Four-color multiplex real-time PCR assay prototype targeting azithromycin resistance mutations in Mycoplasma genitalium

Background

The worldwide expansion of macrolide-resistant Mycoplasma genitalium (MG) in cases of genital infections has led to an increased recurrence rate of these infections after first-line azithromycin treatment. By detecting the presence of azithromycin-resistant MG, the patient’s antibiotic treatment can be targeted and the spread of resistance prevented. With this aim in mind, macrolide-resistance detection kits are helpful tools for the physician.

Methods

Azithromycin resistance mutations in MG are targeted using a four-color multiplex real-time RT-PCR assay. Tested targets include plasmid DNA (as positive controls) as well as macrolide-sensitive and macrolide-resistant genomic DNA from characterized cell lines and clinical samples.

Results

The analytical data presented here were generated from plasmid DNA and genomic RNA/DNA and include adaptation to an internal control, specificity between targets, specificity vs non-MG species, limit of detection (LoD) and interference studies (co-infection and endogenous substances). The clinical data were based on the application of the assay to clinical samples characterized by sequencing.

Conclusions

A new NAAT (nucleic acid amplification test) prototype has been developed in collaboration with the Diagenode s.a. company, this prototype targets MG and azithromycin-resistance mutations in that pathogen.