Analysis of fluoroquinolone-resistance using MIC determination and homology modelling of ParC of contemporary Mycoplasma genitalium strains

Phenotypic antibiotic resistance of Mycoplasma genitalium and its variation between different macrolide resistance-associated mutations

OBJECTIVES

Mycoplasma genitalium, a sexually transmitted bacterium, faces increasing antibiotic resistance, particularly to azithromycin. However, presence of macrolide resistance-associated mutations (MRAMs) does not evidently implicate azithromycin treatment failure. This study aimed to establish an in vitro co-culture system of M. genitalium isolates and perform phenotypic susceptibility testing for different antibiotics, focusing on azithromycin to evaluate genotypic and phenotypic resistance across MRAMs.

METHODS

Urine specimens testing positive for M. genitalium via nucleic acid amplification were co-cultured with Vero cells. Phenotypic susceptibility testing was performed for eight antibiotics. Growth inhibition and MIC of M. genitalium by azithromycin were compared across different MRAMs.

RESULTS

M. genitalium was cultured from 20/40 (50.0%) positive urine samples, with phenotypic susceptibility tested in a subset. MICs ranged as follows: azithromycin (0.008->32 mg/L), levofloxacin (1-4 mg/L), moxifloxacin (<0.25-1 mg/L), sitafloxacin (<0.032-0.25 mg/L), minocycline (<0.25-1 mg/L), doxycycline (<0.125-2 mg/L), spectinomycin (<2.5->25 mg/L) and lefamulin (<0.004-0.063 mg/L). Isolates with A2058T demonstrated 24-, 7-, 15- and 12-fold increases in growth inhibition compared with A2058G at azithromycin concentrations of 4, 8, 16 and 32 mg/L, respectively (P < 0.01). MRAMs ranked from low to high impact on MIC range were as follows: wildtype (0.008-0.016), A2058T (8-32), A2059G (≥32) and A2058G (>32).

CONCLUSIONS

This study revealed that M. genitalium isolates vary in azithromycin-induced growth inhibition across MRAMs, potentially explaining differences in clinical treatment efficacy. Phenotypic susceptibility testing for other antibiotics demonstrated relatively low MICs. Future studies should incorporate clinical treatment efficacy and symptom severity to optimize treatment for M. genitalium.

Virtual screening and molecular dynamics simulations of phytochemicals targeting cofactor-independent phosphoglycerate mutase in antimicrobial-resistant Mycoplasma genitalium

Mycoplasma genitalium (M. genitalium) poses a significant challenge in clinical treatment due to its increasing antimicrobial resistance. This study investigates alternative therapeutic approaches by targeting the cofactor-independent phosphoglycerate mutase (iPGM) enzyme with phytochemicals derived from ethnobotanical plants. In silico screening identified several promising inhibitors, with 2-carboxy-D-arabinitol demonstrating the highest binding affinity (- 9.77 kcal/mol), followed by gluconic acid (- 9.03 kcal/mol) and citric acid (- 8.68 kcal/mol). Further analysis through molecular dynamics (MD) simulations revealed insights into the binding mechanisms and stability of these phytochemicals within the iPGM active site. The MD simulations indicated initial fluctuations followed by stability, with intermittent spikes in RMSD values. The lowest RMSF values confirmed the stability of the ligand-protein complexes. Key residues, including Ser-61, Arg-188, Glu-62, Asp-397, and Arg-260, were found to play crucial roles in the binding and retention of inhibitors within the active pocket. These findings suggest that the identified phytochemicals could serve as novel antimicrobial agents against M. genitalium by effectively inhibiting iPGM activity.

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.

Sitafloxacin- Versus Moxifloxacin-Based Sequential Treatment for Mycoplasma Genitalium Infections: Protocol for a Multicenter, Open-Label Randomized Controlled Trial

BACKGROUND

Mycoplasma genitalium is an emerging sexually transmitted pathogen associated with increasing antibiotic resistance. The current treatment guidelines recommend moxifloxacin-sequential therapy for macrolide-resistant Mgenitalium or strains with unknown resistance profiles. However, it is unclear whether sitafloxacin, a 4th-generation fluoroquinolone antibiotic, is effective against resistant strains.

OBJECTIVE

This study aims to assess and compare the efficacy and safety of sitafloxacin- and moxifloxacin-based treatment regimens for managing Mgenitalium infections.

METHODS

We will conduct this randomized controlled trial at multiple centers in Japan. Eligible participants include adults aged 18 years or older with a confirmed Mgenitalium infection, as determined through the nucleic acid amplification test. Patients will be randomly assigned using a stratified approach based on the treatment facility and infection site. The interventions comprise oral sitafloxacin (200 mg) daily for 7 days (with optional pretreatment of oral doxycycline, 200 mg, daily for up to 7 days), with a control group receiving oral doxycycline (200 mg) daily for 7 days followed by moxifloxacin (400 mg) daily for another 7 days. The primary outcome is the treatment success rate with a superiority margin of 10%, as confirmed through the nucleic acid amplification test. Secondary outcomes encompass changes in the bacterial load at the urogenital or rectal sites and the emergence of posttreatment-resistant mutant strains.

RESULTS

Enrollment commenced in June 2023 and will conclude in December 2024, with findings anticipated by 2025. The expected success rates fall within the range of 80% for sitafloxacin and 42% for moxifloxacin against Mgenitalium carrying the G248T (S83I) mutation, based on previous studies. Accordingly, with a 5% significance level (2-sided) and 80% statistical power, we aim to recruit 50 participants per group, factoring in a 10% expected dropout rate.

CONCLUSIONS

This study will provide valuable insights into the efficacy and safety of sitafloxacin- versus moxifloxacin-based sequential therapy in treating Mgenitalium infections. These findings have the potential to influence clinical guidelines, favoring more effective therapeutic choices. The multicenter approach enhances the robustness of this study. However, a limitation is the potential insufficiency of statistical power to detect posttreatment-resistant mutant strains in each group, rendering posttreatment-resistance mutations a notable concern. In the future, we may need to increase the sample size to enhance power.

TRIAL REGISTRATION

Japan Registry of Clinical Trials (jRCTs031230111); https://jrct.niph.go.jp/en-latest-detail/jRCTs031230111.

INTERNATIONAL REGISTERED REPORT IDENTIFIER (IRRID)

DERR1-10.2196/52565.

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.

Emerging multidrug resistance contributes to treatment failure in Mycoplasma genitalium infected patients in China

The increased treatment failure in patients with sexually transmitted Mycoplasma genitalium infection is associated with antimicrobial resistance. We performed a retrospective survey of antimicrobial clinical outcomes in M. genitalium-infected patients. In addition, we detected macrolide, fluoroquinolone and tetracycline resistance-associated markers to determine their role in treatment failure. The overall incidence of treatment failure was 28.29%, regardless of the drug used. In the present study, the prevalence of macrolide resistance-associated mutations in the 23S rRNA gene was 64%; that of fluroquinolone resistance-associated S83/D87 substitutions in the parC gene was 67.5%; and that of the tetracycline resistance-associated C1192T mutation in the 16S rRNA gene was 22.5%. Furthermore, evidence of dual antimicrobial resistance was found in 46.4% of pretreatment samples, and triple antimicrobial resistance was identified in 9.9%. These findings regarding the emergence of multidrug-resistant strains of M. genitalium in China are concerning and emphasize the importance of guiding M. genitalium treatment with antimicrobial resistance assays.

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.

Prevalence of macrolide and fluoroquinolone resistance-associated mutations in Mycoplasma genitalium in metropolitan and overseas France

Objective

Limited macrolide and fluoroquinolone resistance data are available in France for Mycoplasma genitalium. We performed a multicentre cross-sectional study to investigate the prevalence of macrolide and fluoroquinolone resistance-associated mutations in M. genitalium-positive patients in metropolitan France between 2018 and 2020 and in overseas France in 2018 and 2019.

Methods

Each year, a 1-month prospective collection of M. genitalium-positive specimens was proposed to metropolitan French microbiology diagnostic laboratories, and a similar 3-month collection was proposed to overseas French laboratories. Resistance-associated mutations were detected using commercial kits and sequencing.

Results

A total of 1630 M. genitalium-positive specimens were analysed. In metropolitan France, the prevalence of macrolide resistance-associated mutations ranged between 34.7% (95% CI 29.4% to 40.4%) and 42.9% (95% CI 37.1% to 49.0%) between 2018 and 2020 and was significantly higher in men (95% CI 52.4% to 60.2%) than in women (95% CI 15.9% to 22.2%) (p<0.001). These prevalences were significantly higher than those of 6.1% (95% CI 3.7% to 10.3%) and 14.7% (95% CI 10.9% to 19.6%) observed in overseas France in 2018 and 2019 (p<0.001), where no difference between genders was noted. The prevalence of fluoroquinolone resistance-associated mutations was also significantly higher in metropolitan France (14.9% (95% CI 11.2% to 19.5%) to 16.1% (95% CI 12.1% to 21.2%)) than in overseas France (1.3% (95% CI 0.4% to 3.7%) and 2.6% (95% CI 1.3% to 5.3%) in 2018 and 2019, respectively) (p<0.001), with no difference between men and women regardless of the location.

Conclusion

This study reports the high prevalence of macrolide and fluoroquinolone resistance-associated mutations in M. genitalium in metropolitan France and highlights the contrast with low prevalence in overseas France. In metropolitan France, macrolide resistance-associated mutation prevalence was three times higher in men than in women, which was likely to be driven by the proportion of men who have sex with men. This suggests that gender and sexual practice should also be taken into account for the management of M. genitalium infections.

Molecular Typing Reveals Distinct Mycoplasma genitalium Transmission Networks among a Cohort of Men Who Have Sex with Men and a Cohort of Women in France

Mycoplasma genitalium causes sexually transmitted infecti.ons in men and women. Treatment failures to macrolides and fluoroquinolones have been reported worldwide. Although the mgpB typing method has often been used in M. genitalium-infected men who have sex with men (MSM), limited typing data are available for M. genitalium-infected women. In this study, we aimed to investigate the genetic relationship between M. genitalium strains and their antibiotic resistance profile in a cohort of MSM (86.2% on HIV preexposure prophylaxis [PrEP], 13.8% HIV positive) and a large cohort of women using mgpB/MG309 typing. The mgpB types were determined in 374 samples from 305 women and 65 MSM. Three MSM and one woman had two concurrent or subsequent samples. Macrolide and fluoroquinolone resistance-associated mutations were searched in the 23S rRNA as well as parC and gyrA genes. The mgpB phylogenetic construction revealed three large clusters that differed according to sexual practices and geographical origin of patients. The prevalence of macrolide and fluoroquinolone resistance was significantly higher in MSM compared with women (95.4% vs. 14.1% and 30.6% vs. 7.2%, p < 0.001, respectively). The macrolide resistance spread was polyclonal in both populations, but clonal diffusion of two dual-resistant types was observed in PrEP users in association with high antibiotic pressure and dense connectivity in this population.

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.