Individualised treatment of Mycoplasma genitalium infection—incorporation of fluoroquinolone resistance testing into clinical care

Mycoplasma genitalium infection and resistance-associated mutations to macrolides and fluoroquinolones among high-risk patients in Taiwan

BACKGROUND

Mycoplasma genitalium is an emerging etiology of sexually transmitted infections (STIs) with increasing resistance to antimicrobials. Surveillance on the epidemiology of M. genitalium infection and antimicrobial resistance is warranted.

METHODS

Between September 2021 and August 2023, people with HIV (PWH) and people without HIV (PWoH) at risk of STIs were screened for M. genitalium infection using a multiplex polymerase-chain-reaction assay of specimens collected from the rectum, urethra, oral cavity, and vagina. The prevalences of resistance-associated mutations (RAMs) of M. genitalium to fluoroquinolones, macrolides, and tetracycline were investigated.

RESULTS

During the 2-year study period, 1021 participants were enrolled, including 531 PWH and 490 PWoH. Overall, 83 (8.1%) and 34 (7.6%) participants had M. genitalium infection at baseline and during follow-up, respectively, with the rectum being the most common site of detection (61.5%). With the first course of antimicrobial treatment, 27 of 63 (42.9%) participants with M. genitalium infection were cured during follow-up, including 24 of 58 (41.4%) who received doxycycline monotherapy. The prevalence of RAMs to macrolides, fluoroquinolones, and tetracyclines at baseline were 24.3%, 22.4%, and 7.9%, respectively. Though PWH had more M. genitalium infection (10.2% vs 5.9%, p = 0.01), a higher rate of RAMs to macrolides (41.0% vs 14.7%, p < 0.01) was found in PWoH.

CONCLUSIONS

Among high-risk populations, the prevalence of M. genitalium infection was 8.1%. The overall genotypic resistance of M. genitalium to macrolides and fluoroquinolones was moderately high in Taiwan. Detection of M. genitalium infection and antimicrobial resistance is warranted to ensure resistance-guided antimicrobial treatments to be administered.

Etiological, sociodemographic and clinical characteristics of sexually transmitted infections and M. genitalium resistance in Shenzhen: a multicenter cross-sectional study in China

Introduction

This study aims to determine the etiological, sociodemographic, and clinical characteristics of STIs, and the level of resistance in M. genitalium in Shenzhen, a representative first-tier city of southern China.

Methods

A multicenter cross-sectional study was conducted and 7886 sexually active participants attending STI-related departments were involved from 22 hospitals. Nine STI-related organisms including N. gonorrhoeae, C. trachomatis, T. vaginalis, M. genitalium, HSV-1, HSV-2, M. hominis, U. parvum, and U. urealyticum were screened.

Results

Being single or divorced was associated with increased detection of N. gonorrhoeae, C. trachomatis, M. genitalium, HSV-1, HSV-2 and M. hominis. Lower education level was associated with increased detection of C. trachomatis, HSV-2 and M. hominis. No insurance coverage was an independent risk factor for T. vaginalis, M. hominis and U. parvum positivity. Three resistance-determining regions related to macrolide and fluoroquinolone were sequenced in 154 M. genitalium positive samples, among which 90.3% harbored mutations related to macrolide or fluroquinolone resistance and 67.5% were multidrug-resistant M. genitalium. A2072G in 23S rRNA and Ser83Ile in parC were the most common mutations. M. hominis was associated with manifestations of bacterial vaginosis in female and epididymitis in male.

Conclusions

Single or divorced individuals, those with lower education level and individuals without insurance are higher-risk key populations for STIs. The prevalence of antimicrobial-resistant M. genitalium in Shenzhen is high. Detection of M. hominis increased significantly with lower education level and no health insurance coverage, and it is associated with bacterial vaginosis or epididymitis, indicating that M. hominis deserves further attention.

Antimicrobial treatment and resistance in sexually transmitted bacterial infections

Sexually transmitted infections (STIs) have been part of human life since ancient times, and their symptoms affect quality of life, and sequelae are common. Socioeconomic and behavioural trends affect the prevalence of STIs, but the discovery of antimicrobials gave hope for treatment, control of the spread of infection and lower rates of sequelae. This has to some extent been achieved, but increasing antimicrobial resistance and increasing transmission in high-risk sexual networks threaten this progress. For Neisseria gonorrhoeae, the only remaining first-line treatment (with ceftriaxone) is at risk of becoming ineffective, and for Mycoplasma genitalium, for which fewer alternative antimicrobial classes are available, incurable infections have already been reported. For Chlamydia trachomatis, in vitro resistance to first-line tetracyclines and macrolides has never been confirmed despite decades of treatment of this highly prevalent STI. Similarly, Treponema pallidum, the cause of syphilis, has remained susceptible to first-line penicillin.

Cost-effectiveness of resistance-guided therapy for Mycoplasma genitalium in Australia

The recommended first-line treatment for Mycoplasma genitalium infections is azithromycin. However, the prevalence of macrolide resistance for M. genitalium has increased to more than 50% worldwide. In 2013, Australia introduced a resistance-guided therapy (RGT) strategy to manage M. genitalium infections. This study assesses the cost-effectiveness of the RGT approach compared to no RGT (i.e., without macrolide resistance profile test) in women, men who have sex with men (MSM), and men who have sex with women (MSW) in Australia. We constructed dynamic transmission models of M. genitalium infections in women, MSM, and MSW in Australia, each with a population of 100,000. These models compared the costs and quality-adjusted life-years (QALYs) gained between RGT and no RGT scenarios from a healthcare perspective over ten years. All costs are reported in 2022 Australian dollars (Australian $). In our model, RGT is cost saving in women and MSM, with the incremental net monetary benefit of $1.3 million and $17.9 million, respectively. In MSW, the RGT approach is not cost-effective, with an incremental cost-effectiveness ratio of -$106.96 per QALY gained. RGT is cost saving compared to no RGT for M. genitalium infections in women and MSM, supporting its adoption as the national management strategy for these two population groups.

Antibiotic adjuvants: synergistic tool to combat multi-drug resistant pathogens

The rise of multi-drug resistant (MDR) pathogens poses a significant challenge to the field of infectious disease treatment. To overcome this problem, novel strategies are being explored to enhance the effectiveness of antibiotics. Antibiotic adjuvants have emerged as a promising approach to combat MDR pathogens by acting synergistically with antibiotics. This review focuses on the role of antibiotic adjuvants as a synergistic tool in the fight against MDR pathogens. Adjuvants refer to compounds or agents that enhance the activity of antibiotics, either by potentiating their effects or by targeting the mechanisms of antibiotic resistance. The utilization of antibiotic adjuvants offers several advantages. Firstly, they can restore the effectiveness of existing antibiotics against resistant strains. Adjuvants can inhibit the mechanisms that confer resistance, making the pathogens susceptible to the action of antibiotics. Secondly, adjuvants can enhance the activity of antibiotics by improving their penetration into bacterial cells, increasing their stability, or inhibiting efflux pumps that expel antibiotics from bacterial cells. Various types of antibiotic adjuvants have been investigated, including efflux pump inhibitors, resistance-modifying agents, and compounds that disrupt bacterial biofilms. These adjuvants can act synergistically with antibiotics, resulting in increased antibacterial activity and overcoming resistance mechanisms. In conclusion, antibiotic adjuvants have the potential to revolutionize the treatment of MDR pathogens. By enhancing the efficacy of antibiotics, adjuvants offer a promising strategy to combat the growing threat of antibiotic resistance. Further research and development in this field are crucial to harness the full potential of antibiotic adjuvants and bring them closer to clinical application.

Treatment of bacterial sexually transmitted infections in Europe: gonorrhoea, Mycoplasma genitalium, and syphilis

This review explores the therapeutic challenges of sexually transmitted infections (STI) in Europe, which include increasing antimicrobial resistance and limited progress in drug discovery. We primarily focus on gonorrhoea, Mycoplasma genitalium, and syphilis infections. For gonorrhoea with escalating resistance rates we explore the possibility of combining ceftriaxone with another antibiotic or using alternative antibiotics to mitigate resistance emergence, and we provide insights on the ongoing evaluation of new antimicrobials, like gepotidacin and zoliflodacin. In the case of M. genitalium, which exhibits high resistance rates to first and second-line treatments, we emphasize the importance of resistance-guided therapy in regions with elevated resistance levels, and highlight the limited alternative options, such as pristinamycin and minocycline. Furthermore, we address the challenges posed by syphilis, where the primary treatment consists of penicillin or doxycycline, with challenges arising in neurosyphilis, allergy, pregnancy, and supply shortages and discuss the ongoing evaluation of alternative antimicrobials (e.g., ceftriaxone, cefixime, linezolid). Our findings identify priority actions and provide concrete solutions for long-term effective management of STIs and antimicrobial resistance mitigation.

Detection of macrolide and fluoroquinolone resistance-associated 23S rRNA and parC mutations in Mycoplasma genitalium by nested real-time PCR

Background

Traditional drug susceptibility testing cannot be performed in clinical laboratories due to the slow-growing characteristics of Mycoplasma genitalium when cultured in vitro. Sanger sequencing is the standard method for detecting drug resistance-associated mutations. It has been used in some laboratories to guide the choice of macrolide antibiotics for Mycoplasma genitalium infected patients. Furthermore, resistance to fluoroquinolone has become another emerging clinical challenge.

Objective

Sequencing analysis can detect unknown mutations, but it is time-consuming, requires professional analytical skills and the appropriate testing equipment. The main objective of this study was to establish a nested real-time PCR method for the simultaneous detection of 23S rRNA and parC genotypes in relation to the macrolide and fluoroquinolone resistance.

Results

105 MG-positive samples and 27 samples containing other pathogens were used for validation. The limit of the nested real-time PCR detection was 500 copies/reaction and there was no cross-reaction with Ureaplasma urealyticum, Mycoplasma hominis, Chlamydia trachomatis, Neisseria gonorrhoeae, Human papillomavirus, Herpes simplex virus, Candida albicans and Ureaplasma parvum, but the 23S rRNA assay cross-reacted with Mycoplasma pneumoniae. Compared with sequencing results, the sensitivity of 23S rRNA was 100% (95% CI; 93.3 -100), the specificity was 94.3% (95% CI; 79.4 - 99.0), the overall consistency was 98% (95% CI; 92.5 - 99.7) and kappa value was 0.96 (P < 0.001); the sensitivity of parC was 100% (95% CI; 93.4 - 100), the specificity was 89.7% (95% CI; 71.5 - 97.3) and the overall consistency was 96.9% (95% CI; 90.7 - 99.2) with a kappa value of 0.92 (P < 0.001).

Conclusions

The results of this sensitive and rapid alternative for identifying resistant genotypes of Mycoplasma genitalium are intuitive and easy to interpret, especially for mixed MG populations. Although the relevant 23S rRNA primers need further adjustment, this reliable method would provide an effective diagnostic tool for the selection of antibiotics in clinical practice.

Emerging Antimicrobial Resistance

The burden of emerging antimicrobial resistance (AMR) in the United States is significant and even greater worldwide. Mitigation efforts have decreased the incidence and deaths from antimicrobial-resistant organisms in the United States. Yet more than 2.8 million antimicrobial-resistant infections occur every year and more than 35,000 patients die as a result. Infection prevention and control, data tracking, antimicrobial stewardship, vaccines, therapeutics, diagnostics, and sanitation are all required to decrease AMR threats. In 2019, in the second version of the Centers for Disease Control and Prevention (CDC) report on antibiotic-resistant threats, the agency categorized AMR threats as urgent, serious, concerning, or to be watched. This review will discuss the following aspects of each bacterium in the CDC report: estimated numbers of cases and deaths, identify the better known and impactful mechanisms of resistance, diagnostic testing and its limitations, and current and possible future therapies. This review also presents anatomical pathology case examples that highlight the altered morphology of antibiotic partially treated bacteria in tissues.

Effectiveness of sitafloxacin monotherapy for quinolone-resistant rectal and urogenital Mycoplasma genitalium infections: a prospective cohort study

BACKGROUND

Mycoplasma genitalium has a tendency to develop macrolide and quinolone resistance.

OBJECTIVES

We investigated the microbiological cure rate of a 7 day course of sitafloxacin for the treatment of rectal and urogenital infections in MSM.

PATIENTS AND METHODS

This open-label, prospective cohort study was conducted at the National Center for Global Health and Medicine, Tokyo, Japan from January 2019 to August 2022. Patients with M. genitalium urogenital or rectal infections were included. The patients were treated with sitafloxacin 200 mg daily for 7 days. M. genitalium isolates were tested for parC, gyrA and 23S rRNA resistance-associated mutations.

RESULTS

In total, 180 patients (median age, 35 years) were included in this study, of whom 77.0% (97/126) harboured parC mutations, including 71.4% (90/126) with G248T(S83I) in parC, and 22.5% (27/120) harboured gyrA mutations. The median time to test of cure was 21 days. The overall microbiological cure rate was 87.8%. The cure rate was 100% for microbes harbouring parC and gyrA WTs, 92.9% for microbes harbouring parC G248T(S83I) and gyrA WT, and 41.7% for microbes harbouring parC G248T(S83I) and gyrA with mutations. The cure rate did not differ significantly between urogenital and rectal infection (P = 0.359).

CONCLUSIONS

Sitafloxacin monotherapy was highly effective against infection caused by M. genitalium, except strains with combined parC and gyrA mutations. Sitafloxacin monotherapy can be used as a first-line treatment for M. genitalium infections in settings with a high prevalence of parC mutations and a low prevalence of gyrA mutations.

gyrA Mutations in Mycoplasma genitalium and Their Contribution to Moxifloxacin Failure: Time for the Next Generation of Resistance-Guided Therapy

BACKGROUND

Although single nucleotide polymorphisms (SNPs) in Mycoplasma genitalium parC contribute to fluoroquinolone treatment failure, data are limited for the homologous gene, gyrA. This study investigated the prevalence of gyrA SNPs and their contribution to fluoroquinolone failure.

METHODS

Samples from 411 patients (male and female) undergoing treatment for M. genitalium infection (Melbourne Sexual Health Centre, March 2019-February 2020) were analyzed by Sanger sequencing (gyrA and parC). For patients treated with moxifloxacin (n = 194), the association between SNPs and microbiologic treatment outcome was analyzed.

RESULTS

The most common parC SNP was G248T/S83I (21.1% of samples), followed by D87N (2.3%). The most common gyrA SNP was G285A/M95I (7.1%). Dual parC/gyrA SNPs were found in 8.6% of cases. One third of infections harboring parC G248T/S83I SNP had a concurrent SNP in gyrA conferring M95I. SNPs in gyrA cooccurred with parC S83I variations. Treatment failure was higher in patients with parC S83I/gyrA dual SNPs when compared with infections with single S83I SNP alone from analysis of (1) 194 cases in this study (81.2% vs 45.8%, P = .047), and (2) pooled analysis of a larger population of 535 cases (80.6% vs 43.2%; P = .0027), indicating a strong additive effect.

CONCLUSIONS

Compared with parC S83I SNP alone, M. genitalium infections with dual mutations affecting parC/gyrA had twice the likelihood of failing moxifloxacin. Although antimicrobial resistance varies by region globally, these data indicate that gyrA should be considered as a target for future resistance assays in Australasia. We propose a strategy for the next generation of resistance-guided therapy incorporating parC and gyrA testing.

Mycoplasma genitalium antibiotic resistance-associated mutations in genital and extragenital samples from men-who-have-sex-with-men attending a STI clinic in Verona, Italy

Background

Mycoplasma genitalium (MG) is one of the most warning emerging sexually transmitted pathogens also due to its ability in developing resistance to antibiotics. MG causes different conditions ranging from asymptomatic infections to acute mucous inflammation. Resistance-guided therapy has demonstrated the best cure rates and macrolide resistance testing is recommended in many international guidelines. However, diagnostic and resistance testing can only be based on molecular methods, and the gap between genotypic resistance and microbiological clearance has not been fully evaluated yet. This study aims at finding mutations associated with MG antibiotic resistance and investigating the relationship with microbiological clearance amongst MSM.

Methods

From 2017 to 2021, genital (urine) and extragenital (pharyngeal and anorectal swabs) biological specimens were provided by men-who-have-sex-with-men (MSM) attending the STI clinic of the Infectious Disease Unit at the Verona University Hospital, Verona, Italy. A total of 1040 MSM were evaluated and 107 samples from 96 subjects resulted positive for MG. Among the MG-positive samples, all those available for further analysis (n=47) were considered for detection of mutations known to be associated with macrolide and quinolone resistance. 23S rRNA, gyrA and parC genes were analyzed by Sanger sequencing and Allplex™ MG and AziR Assay (Seegene).

Results

A total of 96/1040 (9.2%) subjects tested positive for MG in at least one anatomical site. MG was detected in 107 specimens: 33 urine samples, 72 rectal swabs and 2 pharyngeal swabs. Among them, 47 samples from 42 MSM were available for investigating the presence of mutations associated with macrolide and quinolone resistance: 30/47 (63.8%) showed mutations in 23S rRNA while 10/47 (21.3%) in parC or gyrA genes. All patients with positive Test of Cure (ToC) after first-line treatment with azithromycin (n=15) were infected with 23S rRNA-mutated MG strains. All patients undergoing second-line moxifloxacin treatment (n=13) resulted negative at ToC, even those carrying MG strains with mutations in parC gene (n=6).

Conclusion

Our observations confirm that mutations in 23S rRNA gene are associated with azithromycin treatment failure and that mutations in parC gene alone are not always associated with phenotypic resistance to moxifloxacin. This reinforces the importance of macrolide resistance testing to guide the treatment and reduce antibiotic pressure on MG strains.

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.

Potential therapeutic targets for combating Mycoplasma genitalium

Mycoplasma genitalium (M. genitalium) has emerged as a sexually transmitted infection (STI) all over the world in the last three decades. It has been identified as a cause of male urethritis, and there is now evidence that it also causes cervicitis and pelvic inflammatory disease in women. However, the precise role of M. genitalium in diseases such as pelvic inflammatory disease, and infertility is unknown, and more research is required. It is a slow-growing organism, and with the advent of the nucleic acid amplification test (NAAT), more studies are being conducted and knowledge about the pathogenicity of this organism is being elucidated. The accumulation of data has improved our understanding of the pathogen and its role in disease transmission. Despite the widespread use of single-dose azithromycin in the sexual health field, M. genitalium is known to rapidly develop antibiotic resistance. As a result, the media frequently refer to this pathogen as the "new STI superbug." Despite their rarity, antibiotics available today have serious side effects. As the cure rates for first-line antimicrobials have decreased, it is now a challenge to determine the effective antimicrobial therapy. In this review, we summarise recent M. genitalium research and investigate potential therapeutic targets for combating this pathogen.

Mycoplasma genitalium infection in the female reproductive system: Diseases and treatment

Mycoplasma genitalium is a newly emerged sexually transmitted disease pathogen and an independent risk factor for female cervicitis and pelvic inflammatory disease. The clinical symptoms caused by M. genitalium infection are mild and easily ignored. If left untreated, M. genitalium can grow along the reproductive tract and cause salpingitis, leading to infertility and ectopic pregnancy. Additionally, M. genitalium infection in late pregnancy can increase the incidence of preterm birth. M. genitalium infections are often accompanied by co-infection with other sexually transmitted pathogens (Chlamydia trachomatis, Neisseria gonorrhoeae, and Trichomonas vaginalis) and viral infections (Human Papilloma Virus and Human Immunodeficiency Virus). A recent study suggested that M. genitalium plays a role in tumor development in the female reproductive system. However, few studies endorsed this finding. In recent years, M. genitalium has evolved into a new "superbug" due to the emergence of macrolide-and fluoroquinolone-resistant strains leading to frequent therapy failures. This review summarizes the pathogenic characteristics of M. genitalium and the female reproductive diseases caused by M. genitalium (cervicitis, pelvic inflammatory disease, ectopic pregnancy, infertility, premature birth, co-infection, reproductive tumors, etc.), as well as its potential relationship with reproductive tumors and clinical treatment.

Clinical Performance of Three Commercial Molecular Diagnostic Assays for the Detection of Fluoroquinolone Resistance-Associated Mutations in Mycoplasma genitalium

The high prevalence of macrolide resistance in Mycoplasma genitalium results in an increased reliance on moxifloxacin, the second-line treatment; however, moxifloxacin resistance has also emerged. Because assays that can detect fluoroquinolone resistance-associated mutations will be useful for the management of macrolide-resistant M. genitalium infections, we evaluated the performance of three commercial assays (the Allplex MG & MoxiR Assay [Seegene], LightMix Modular parC kit [TIBMOLBIOL], and MGMO qPCR [NYtor) in comparison with parC gene Sanger sequencing used as the reference. Between January 2018 and December 2020, remnants of M. genitalium-positive clinical specimens received at the French National Reference Center for Bacterial Sexually Transmitted Infections were collected if a Sanger sequencing result was obtained for the parC gene. Overall, 368 M. genitalium-positive specimens were assessed. The clinical sensitivities for the detection of the ParC mutations that are likely of clinical significance were 91.8% (95% CI = 83.2 to 96.2), 98.6% (95% CI = 92.4 to 99.8), and 94.4% (95% CI = 86.6 to 97.8) for the Allplex MG & MoxiR, LightMix Modular parC, and MGMO qPCR kits, respectively, with no significant difference between the three kits. The clinical specificity of the Allplex MG & MoxiR and MGMO qPCR kits was 100% (95% CI = 97.7 to 100 and 98.7 to 100, respectively), which was significantly higher than the specificity of the LightMix Modular parC kit of 95.4% (95%CI = 92.3 to 97.3), for which the interpretation of melting curves may be misleading. These kits should be useful for the selection of antimicrobials in macrolide-resistant M. genitalium infections, although further developments may be necessary because parC mutations involved in fluoroquinolone resistance have not been precisely determined.

Increases in the Macrolide Resistance of Mycoplasma genitalium and the Emergence of the A2058T Mutation in the 23S rRNA Gene: Clonal Spread?

The management of Mycoplasma genitalium sexually transmitted infection (STI) is hindered by increasing resistance to the recommended antibiotics, macrolides and quinolones, worldwide. In Gipuzkoa (Basque Country, Spain), macrolide and quinolone resistance rates in 2014−2018 were reported as <20% and <10%, respectively. The aims of this study were to compare these rates with those in 2019−2021 and analyse the genetic and epidemiological features of the strains and cases associated with striking changes in the resistance trends. Resistance to macrolides (n = 1019) and quinolones (n = 958) was studied, analysing mutations in 23S rRNA and parC/gyrA genes, respectively. The rate of macrolide resistance increased from 17.3% in 2014−2018 to 32.1% in 2019−2021, as much in the more prevalent A2058/2059G mutations (16.6−27.8%) as in the emergent A2058T mutations (0.5−4.1%) but with differences in the odds ratios and the relative risk increase between A2058T and A2058/2059G mutations. MG191 adhesin and MG309 lipoprotein of the 27 emergent strains detected with A2058T mutations were amplified, sequenced, and typed using phylogenetic and variable number tandem repeat analysis, respectively. Genetic clonal spread was ruled out, but most of the A2058T cases were men who had sex with men (24/27) with a history of STI and antibiotic treatments (19/27). No changes were observed in quinolone resistance trends, but the rate of resistance to both antibiotics rose from 2.9% to 8.3%, especially in cases with A2058T mutations. The genetic characterisation of strains and epidemiological surveillance of cases are needed to detect populations at increased risk of treatment failure in this infection.

Rapid Detection of Antimicrobial Resistance in Mycoplasma genitalium by High-Resolution Melting Analysis with Unlabeled Probes

With looming resistance to fluoroquinolones in Mycoplasma genitalium, public health control strategies require effective antimicrobial resistance (AMR) diagnostic methods for clinical and phenotypic AMR surveillance. We developed a novel AMR detection method, MGparC-AsyHRM, based on the combination of asymmetric high-resolution melting (HRM) technology and unlabeled probes, which simultaneously performs M. genitalium identification and genotypes eight mutations in the parC gene that are responsible for most cases of fluoroquinolone resistance. These enhancements expand the traditional HRM from the conventional detection of single-position mutations to a method capable of detecting short fragments with closely located AMR positions with a high diversity of mutations. Based on the results of clinical sample testing, this method produces an accordance of 98.7% with the Sanger sequencing method. Furthermore, the specificity for detecting S83I, S83N, S83R, and D87Y variants, the most frequently detected mutations in fluoroquinolone resistance, was 100%. This method maintained a stable and accurate performance for genomic copies at rates of ≥20 copies per reaction, demonstrating high sensitivity. Additionally, no specific cross-reactions were observed when testing eight common sexually transmitted infection (STI)-related agents. Notably, this work highlights the significant potential of our method in the field of AMR testing, with the results suggesting that our method can be applied in a range of scenarios and to additional pathogens. In summary, our method enables high throughput, provides excellent specificity and sensitivity, and is cost-effective, suggesting that this method can be used to rapidly monitor the molecular AMR status and complement current AMR surveillance. IMPORTANCE Mycoplasma genitalium was recently added to the antimicrobial-resistant (AMR) threats "watch list" of the U.S. Centers for Disease Control and Prevention because this pathogen has become extremely difficult to treat as a result of increased resistance. M. genitalium is also difficult to culture, and therefore, molecule detection is the only method available for AMR testing. In this work, we developed a novel AMR detection method, MGparC-AsyHRM, based on the combination of asymmetrical HRM technology and unlabeled probes, and it simultaneously performs M. genitalium identification and genotypes eight mutations in the parC gene that are responsible for most cases of fluoroquinolone resistance. The MGparC-AsyHRM method is a high-throughput, low-cost, simple, and culture-free procedure that can enhance public health and management of M. genitalium infections and AMR control, providing a strong complement to phenotypic AMR surveillance to address the spread of fluoroquinolone resistance.

Novel probe-based melting curve assays for the characterization of fluoroquinolone resistance in Mycoplasma genitalium

BACKGROUND

Mycoplasma genitalium infection is a sexually transmitted infection that has rapidly become resistant to mainstay treatments. While individualized treatment approaches have been recommended and adopted for macrolides, individualized therapy for fluoroquinolones has not yet been explored, due to a lack of commercial molecular assays and a lack of confidence in specific mutations associated with resistance. In another recent study, we defined a clear role and diagnostic utility in focusing on the absence of resistance mutations to inform microbial cure with fluoroquinolone antimicrobials.

METHODS

We developed two proof-of-concept molecular tests that focus on detection of M. genitalium and characterization of WT parC sequences that are strongly linked to fluoroquinolone susceptibility.

RESULTS

We screened a total of 227 M. genitalium-positive samples using novel molecular beacon and dual hybridization probe assays. These assays were able to detect M. genitalium and characterize fluoroquinolone susceptibility in 143/227 (63%) samples, based on clear differences in melting peak temperatures. The results of these molecular assays were in 100% agreement with 'gold standard' Sanger sequencing. Additionally, WT parC sequences were readily distinguished from M. genitalium samples harbouring parC mutations of known or suspected clinical significance. The ability of the assays to successfully characterize fluoroquinolone susceptibility and resistance was reduced in low M. genitalium load samples.

CONCLUSIONS

These proof-of-concept assays have considerable potential to improve individualized treatment approaches and rationalize tests of cure for M. genitalium infection. The ability to initiate individualized treatment in up to two-thirds of cases will enhance antimicrobial stewardship for this challenging pathogen.

parC Variants in Mycoplasma genitalium: Trends over Time and Association with Moxifloxacin Failure

Prevalence, trends, and treatment outcome estimates were generated for parC variants in macrolide-resistant Mycoplasma genitalium. Among 539 cases, the most common amino acid change was S83I, which increased from 13% in 2012 to 2013, to 23% in 2019 to 2020 (P_trend = 0.046). From 381 moxifloxacin treatments, failure occurred in 58.7% (95% confidence interval [CI], 46.7 to 69.9) of cases with S83I. Other changes affecting S83 or D87 were uncommon and minor contributors to failure. The absence of S83I was highly predictive of moxifloxacin cure (96.4%; 95% CI, 93.7 to 98.2), highlighting diagnostic potential.