Evaluation of TIB Molbiol LightMix® assays for detection of Mycoplasma genitalium and key resistance mutations for macrolides and fluoroquinolones.

The LightMix® Modular Mycoplasma Macrolide and LightMix® Modular parC Fluoroquinolone Resistance assays (TIB Molbiol) were evaluated using sequential Mycoplasma genitalium positive (n = 125) and negative (n = 93) clinical samples. Results were compared to the results of an established commercial assay (ResistancePlus MG assay, SpeeDx Pty Ltd) or Sanger sequencing (for parC). Detection of M. genitalium by the TIB Molbiol assay had a high agreement with the reference assay, with a positive percent agreement (PPA) of 97.6 [95% confidence interval (CI): 93.1-99.5] and negative percent agreement (NPA) of 95.7 (95% CI: 89.5-98.8). From 105 positive samples, macrolide resistance detection had a PPA of 100% (95% CI: 93.7-100) and NPA of 81.3% (95% CI: 67.4-91.1). For the detection of fluroquinolone resistance mutation G248T/S83I or "other mutation" in the quinolone resistance determinant region, from 95 samples there was 100% (95% CI: 86.3-100) sensitivity and 100% (95% CI: 94.5-100) specificity. The understanding of the basis for fluoroquinolone treatment failure is still developing; it is therefore important to use the output of parC-based resistance assays with caution to avoid the inappropriate use of antibiotic therapies, especially considering the limited number of alternative treatments.

Quantitation of Mycoplasma genitalium using droplet digital PCR.

Mycoplasma genitalium is a sexually transmitted infection with increasing concerns around antimicrobial resistance. Droplet digital PCR (ddPCR) is a rapid quantification method with high precision that may be useful for absolute quantitation of bacteria in samples. This study aimed to develop a ddPCR assay for the quantification of M. genitalium. ddPCR targeting the gene mgpB was established and analysed using the QX100 ddPCR system. The assay was evaluated against quantitated DNA standards, and then in comparison to an established quantitative PCR performed on the Lightcycler 480 II. DNA template of increasing complexity was used, including synthetic double stranded DNA, DNA extracts from laboratory-cultured M. genitalium strains (n = 17) and DNA from M. genitalium-positive clinical samples (n = 21). There was a strong correlation between ddPCR concentration estimates and measured DNA standards (r2 = 0.997), and between ddPCR and qPCR quantitation for different templates (r2 ranging from 0.953 to 0.997). ddPCR reliably detected template in a range from <10 copies per reaction to >104 copies per reaction and demonstrated linearity over dilution series. Concentration estimates by ddPCR were reproducibly less than those determine by qPCR. ddPCR demonstrated precise and reproducible quantitation of M. genitalium with a variety of templates.

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.

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 (Ptrend = 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.

Impact of 16S rRNA Single Nucleotide Polymorphisms on Mycoplasma genitalium Organism Load with Doxycycline Treatment.

Doxycycline targets the 16S rRNA and is widely used for the treatment of sexually transmitted infections. While it is not highly effective at eradicating Mycoplasma genitalium infections, it can reduce organism load. The aim of this study was to investigate the association between single nucleotide polymorphisms (SNPs) in the 16S rRNA gene of M. genitalium and change in organism load. M. genitalium samples were collected from 56 men prior to commencing doxycycline and at a median of 13 of 14 doses. These were sequenced for the 16S rRNA, and the association between 16S rRNA SNPs and change in organism load was determined. 16S rRNA sequences were available for 52/56 (92.9%) M. genitalium-infected men, of which 20 (38.5%) had an undetectable load, 26 (50.0%) had a decrease in M. genitalium load (median change of 105-fold), and 6 (11.5%) had an increase in load (median change of 5-fold). The most common SNPs identified were A742G (10/52 [19.2%]), GG960-961TT/C (7/52 [13.5%]), and C1435T (28/52 [53.8%]) (M. genitalium numbering). None were associated with a change in organism load (P = 0.76, 0.16, and 0.98, respectively). Using pooled published data from 28 isolates, no clear relationship between the SNPs and doxycycline MIC was identified. In conclusion, the low efficacy of doxycycline against M. genitalium does not appear to be due to variation in the 16S rRNA gene.

Combination Therapy for Mycoplasma genitalium, and New Insights Into the Utility of parC Mutant Detection to Improve Cure.

BACKGROUND: Mycoplasma genitalium (MG) infection is challenging to cure because of rising antimicrobial resistance and limited treatment options. METHODS: This was a prospective evaluation of the efficacy and tolerability of resistance-guided combination antimicrobial therapy for MG treatment at Melbourne Sexual Health Centre (August 2019-December 2020). All patients received 7 days of doxycycline before combination therapy based on the macrolide-resistant profile. Macrolide-susceptible infections received combination doxycycline + azithromycin (1 g, day 1; 500 mg, days 2-4) and macrolide-resistant infections combination doxycycline + moxifloxacin (400 mg daily for 7 days). Adherence and adverse effects were recorded at test-of-cure, recommended 14-28 days after antimicrobial completion. Sequencing was performed to determine the prevalence of single nucleotide polymorphisms (SNPs) in the parC gene and their association with moxifloxacin treatment outcomes in macrolide-resistant infections. RESULTS: Of 100 patients with macrolide-susceptible MG treated with doxycycline + azithromycin, 93 were cured (93.0%; 95% confidence interval [CI], 86.1-97.1). Of 247 patients with macrolide-resistant MG receiving doxycycline + moxifloxacin, 210 were cured (85.0%; 95% CI, 80.0-89.2). parC sequencing was available for 164 (66%) macrolide-resistant infections; 29% had SNPs at parC S83 or D87 (23% S83I). The absence of SNPs at parC S83/D87 was associated with 98.3% cure (95% CI, 93.9-99.8) following doxycycline + moxifloxacin. The presence of the parC S83I-SNP was associated with failure in 62.5% (95% CI, 45.8-77.3). Side effects were common (40%-46%) and predominantly mild and gastrointestinal. CONCLUSIONS: Combination doxycycline + azithromycin achieved high cure for macrolide-susceptible infections. However, in the context of a high prevalence of the parC S83I mutation (23%) in macrolide-resistant infections, doxycycline + moxifloxacin cured only 85%. Infections that were wild-type for S83/D87 experienced high cure following doxycycline + moxifloxacin, supporting the use of a parC-resistance/susceptibility testing strategy in clinical care.

The clinical indications for testing women for Mycoplasma genitalium.

BACKGROUND: While the contribution of Mycoplasma genitalium (MG) to symptoms in men is well described, less is known about its association with common genital symptoms in women. We aimed to determine the prevalence of MG and macrolide resistance, and its association with common genital symptoms in women attending a sexual health service, to inform indications for testing and clinical practice. METHODS: We undertook a cross-sectional study of symptomatic and asymptomatic women attending Melbourne Sexual Health Centre (MSHC), between April 2017 and April 2019. Women were tested for MG and macrolide resistance, Chlamydia trachomatis (CT), Neisseria gonorrhoeae, Trichomonas vaginalis, bacterial vaginosis and vulvovaginal candidiasis. Women completed a questionnaire on symptoms, and symptomatic women underwent examination. The prevalence of MG (and macrolide resistance) and other genital infections was calculated with 95% CIs, and associations between these outcomes and specific genital symptoms were examined using logistic regression. RESULTS: Of 1318 women, 83 (6%, 95% CI: 5% to 8%) had MG, of which 39 (48%, 95% CI: 36% to 59%) had macrolide-resistant MG; 103 (8%, 95% CI: 6% to 9%) women had CT. MG prevalence was similar in asymptomatic (10 of 195; 5%) and symptomatic (73 of 1108; 7%) women, p=0.506. MG was associated with mucopurulent cervicitis on examination (adjusted OR=4.38, 95% CI: 1.69 to 11.33, p=0.002), but was not associated with other specific genital symptoms or signs. CONCLUSIONS: MG was as common as CT among women attending MSHC. MG was not associated with genital symptoms, but like CT, was significantly associated with cervicitis. These data provide evidence that routine testing for MG in women with common genital symptoms is not indicated. The presence of macrolide resistance in 48% of women supports use of resistance-guided therapy.

Prevalence of Mycoplasma genitalium fluoroquinolone-resistance markers, and dual-class-resistance markers, in asymptomatic men who have sex with men.

Introduction. Failure of fluoroquinolones, the principal treatment option for macrolide-resistant Mycoplasma genitalium infections, has recently emerged. This is of particular concern for men who have sex with men (MSM), who have high proportions of macrolide-resistant M. genitalium infections. Treatment failure with moxifloxacin is likely the result of single nucleotide polymorphisms (SNPs) in parC, whilst concurrent gyrA mutations may play a role.Gap Statement. The levels of fluoroquinolone resistance and dual-class (i.e. macrolide and fluoroquinolone) resistance in M. genitalium among asymptomatic MSM is unknown.Aim. To (i) determine the proportion of fluoroquinolone resistance and dual-class resistance in M. genitalium infections among asymptomatic MSM, (ii) explore any clinical and behavioural associations with fluoroquinolone resistance, and (iii) determine the distribution of antibiotic resistance among M. genitalium mgpB sequence types (STs).Methodology. M. genitalium positive samples (N=94) were obtained from 1001 asymptomatic MSM enrolled in a study at Melbourne Sexual Health Centre (Carlton, Australia) between August 2016 and September 2017. Sanger sequencing was performed to determine the proportion of M. genitalium infections with SNPs in parC that have previously been associated with failure of moxifloxacin (corresponding to amino changes S83I, D83R, D87Y and D87N) and in gyrA (corresponding to amino acid changes M95I, D99N, D99Y and D99G). Associations between clinical/behavioural factors and parC SNPs were examined. Strain typing was performed by sequencing a portion of the mgpB gene.Results. The proportion of MSM with infections harbouring parC and gyrA SNPs was 13.0 % [95 % confidence interval (CI): 6.8-23.2 %] and 4.7 % (95 % CI: 1.1-13.4 %), respectively; dual-class resistance was 13.0 %. No significant clinical/behavioural associations were found. Antibiotic resistance was not restricted to specific mgpB STs.Conclusion. One in eight (13 %) of asymptomatic MSM with M. genitalium had an infection with dual-class-resistance mutations. Typing by mgpB sequence suggested fluoroquinolone resistance is arising from independent mutation events. This study illustrates that asymptomatic MSM may act as a reservoir for antibiotic-resistant M. genitalium.

Detection of parC gene mutations associated with quinolone resistance in Mycoplasma genitalium: evaluation of a multiplex real-time PCR assay.

Introduction. Increasing levels of antibiotic resistance are complicating treatment for the sexually transmitted pathogen Mycoplasma genitalium. Resistance to fluoroquinolones is associated with mutations in the parC gene. Although the precise mutations conferring resistance are not fully understood, the single nucleotide polymorphism (SNP) G248T/S83I is most implicated.Aim. To evaluate the performance of the MG+parC(beta2) assay (SpeeDx, Australia), which detects single nucleotide polymorphisms (SNPs) in the parC gene at amino acid position S83 (A247C/S83R, G248T/S83I, G248A/S83N) and D87 (G259A/D87N, G259T/D87Y, G259C/D87H).Methods. Clinical samples were analysed by MG+parC(beta2) assay and results compared to Sanger sequencing. Sensitivity, specificity, and predictive value for treatment failure were calculated.Results. From analysis of 205 samples, the MG+parC(beta2) assay performed with a high sensitivity 98.2% (95% CI:90.3-100) and specificity 99.3% (95% CI:96.3-100) for parC SNP detection with a kappa of 0.97 (95% CI:0.94-1.00). The predictive value of G248T/S83I detection (the most common SNP, prevalence of 13% in the study population) was analysed with respect to treatment failure (patients received sequential doxycycline-moxifloxacin). The positive-predictive-value for moxifloxacin failure after detection of S83I was only 44% (95% CI:24.4-65.1), while negative-predictive-value was high at 96.9% (95% CI:92.7-99.0), suggesting that other SNPs are contributing to resistance.Conclusion. MG+parC(beta2) performed with high concordance compared to Sanger sequencing. Such qPCR assays can assist in understanding causes of treatment failure, inform the development of diagnostic assays, and can be applied to surveillance of mutations in populations. Due to an incomplete understanding of the basis for fluoroquinolone resistance, such tests do not appear to be ready for clinical application.

Are Mycoplasma hominis, Ureaplasma urealyticum and Ureaplasma parvum Associated With Specific Genital Symptoms and Clinical Signs in Nonpregnant Women?

BACKGROUND: There is limited evidence supporting an association between Mycoplasma hominis, Ureaplasma urealyticum, and Ureaplasma parvum with symptoms or disease in nonpregnant women. However, testing and reporting of these organisms frequently occurs, in part due to their inclusion in multiplex-PCR assays for sexually transmitted infection (STI) detection. We investigated if M. hominis, U. urealyticum, and U. parvum were associated with symptoms and/or signs in nonpregnant women attending a sexual health service. METHODS: Eligible women attending the Melbourne Sexual Health Centre completed a questionnaire regarding sexual practices and symptoms. Symptomatic women underwent examination. Women were assessed for bacterial vaginosis (BV) and vulvovaginal candidiasis (VVC), and tested for M. hominis, U. urealyticum, and U. parvum, and 4 nonviral STIs using a commercial multiplex-PCR. RESULTS: 1272 women were analyzed. After adjusting for STIs and VVC, M. hominis was associated with abnormal vaginal discharge (aOR = 2.70, 95%CI:1.92-3.79), vaginal malodor (aOR = 4.27, 95%CI:3.08-5.91), vaginal pH > 4.5 (aOR = 4.27, 95%CI:3.22-5.66), and presence of clue cells (aOR = 8.08, 95%CI:5.68-11.48). Ureaplasma spp. were not associated with symptoms/signs. Bacterial vaginosis was strongly associated with M. hominis (aOR = 8.01, 95%CI:5.99-10.71), but was not associated with either Ureaplasma spp. In stratified analyses, M. hominis was associated with self-reported vaginal malodor and clinician-recorded vaginal discharge in women with BV, but not with symptoms/signs in women without BV. CONCLUSIONS: Only M. hominis was associated with symptoms/signs, and these were manifestations of BV. Importantly, M. hominis was not associated with symptoms/signs in women without BV. These findings do not support routine testing for M. hominis, U. urealyticum, and U. parvum in nonpregnant women.

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.

Doxycycline and Sitafloxacin Combination Therapy for Treating Highly Resistant Mycoplasma genitalium.

Antimicrobial-resistant Mycoplasma genitalium is becoming increasingly common and creating major treatment challenges. We present early data on combination therapy with doxycycline and sitafloxacin to treat highly resistant M. genitalium. We found the regimen was well tolerated and cured 11/12 infections that had failed prior regimens with moxifloxacin and pristinamycin.

Moxifloxacin and Sitafloxacin Treatment Failure in Mycoplasma genitalium Infection: Association with parC Mutation G248T (S83I) and Concurrent gyrA Mutations.

BACKGROUND: The basis of fluoroquinolone treatment failure for Mycoplasma genitalium is poorly understood. METHODS: To identify mutations associated with failure we sequenced key regions of the M. genitalium parC and gyrA genes for patients undergoing sequential therapy with doxycycline-moxifloxacin (201 patients, including 21 with failure) or doxycycline-sitafloxacin (126 patients, including 13 with failure). RESULTS: The parC G248T/S83I mutation was more common among patients with failed sequential doxycycline-moxifloxacin (present in 76.2% of failures vs 7.8% cures, P < .001) or doxycycline-sitafloxacin (50% vs 16.8%, respectively; P = .01) treatment. Doxycycline-sitafloxacin was more efficacious than doxycycline-moxifloxacin against infections carrying the parC mutation conferring S83I amino acid change. Treatment was more likely to fail in these infections if they had a concurrent gyrA mutation (M95I or D99N) (P = .07 for doxycycline-moxifloxacin group and P = .009 for doxycycline-sitafloxacin group), suggesting an additive effect. CONCLUSIONS: This study indicates that parC G248T/S83I mutations contribute to failure of moxifloxacin and sitafloxacin, and the findings will inform the development of quinolone resistance assays needed to ensure optimal selection of antimicrobials for M. genitalium.

Multicenter Clinical Evaluation of a Novel Multiplex Real-Time PCR (qPCR) Assay for Detection of Fluoroquinolone Resistance in Mycoplasma genitalium.

Mycoplasma genitalium causes a common sexually transmitted infection with a marked propensity to develop antimicrobial resistance. As few treatment options exist, this poses significant challenges to clinicians. Recent diagnostic advances have resulted in tests that report the simultaneous detection of M. genitalium and any resistance to macrolides, the first-line treatment. This allows for therapy to be tailored to the individual, thereby optimizing treatment outcomes. However, resistance to fluoroquinolones, the second-line treatment, is increasing in M. genitalium In this study, we describe a new assay, MG+parC (beta), which simultaneously reports the detection of M. genitalium and five parC mutations that have been associated with resistance to fluoroquinolones. These mutations affect the amino acid sequence of ParC at residues S83R (A247C), S83I (G248T), D87N (G259A), D87Y (G259T), and D87H (G259C). The study tested the MG+parC (beta) assay with 202 M. genitalium-positive clinical samples from Australia (n = 141) and Spain (n = 61). Compared to Sanger sequencing, the assay performed with a kappa value of 0.985 (95% confidence interval [CI], 0.955 to 1.000), with a mutation detection sensitivity of 97.6% (95% CI, 87.4 to 99.9), and specificity of 100.0% (95% CI, 97.7 to 100.0). Fluoroquinolone resistance-associated mutations in parC targeted by the assay were more prevalent among the Australian cohort (23.4% [95% CI,16.3 to 31.8]) compared to the Spanish population (8.8% [95% CI, 2.9% to 19.3%]) (P = 0.019). The MG+parC (beta) kit is a simple and reliable method for simultaneous detection of M. genitalium and fluoroquinolone resistance-associated mutations in clinical settings. This novel diagnostic tool may extend the utility of the second line of antimicrobial therapies in M. genitalium infection.

Analysis of Infection Loads in Mycoplasma genitalium Clinical Specimens by Use of a Commercial Diagnostic Test.

Mycoplasma genitalium is a common sexually transmitted infection with a propensity to acquire resistance to commonly used antimicrobial therapies. Bacterial load has been linked to patient symptoms and the success of treatment. In this study, we demonstrate methodology to estimate load from routine diagnostic assays using the ResistancePlus MG test (SpeeDx Pty Ltd., Australia). The method gave comparable quantitation to an M. genitalium-specific 16S rRNA quantitative PCR (qPCR; Spearman r = 0.94) for the samples analyzed (n = 499, including urine and swab types as detailed below) and was, therefore, employed to analyze typical load levels for samples in a diagnostic laboratory (total of 1,012 tests). When stratified by sample type, female urine (median, 826 genomes/ml) had the lowest load. This was significantly lower than median loads for all other sample types (male urine [6.91 × 103 genomes/ml], anal swabs [5.50 × 103], cervical swabs [8.15 × 103], endocervical swabs [3.97 × 103], and vaginal swabs [6.95 × 103]) (P < 0.0001). There were no significant differences in load estimates between the other sample types. Reproducibility of load estimates conducted on the same samples was high (r > 0.85). In conclusion, this methodology to provide load estimates for M. genitalium can be easily integrated into routine diagnostic laboratory workflow. Given the association between organism load, symptoms, and treatment success, load assessment has future diagnostic potential.