Abstract
Objective To estimate the prevalence of Mycoplasma genitalium in Toronto, Ont; detect mutations associated with macrolide and fluoroquinolone resistance; and describe treatment outcomes.
Design Prospective, cross-sectional study.
Setting A sexual health clinic in Toronto.
Participants A consecutive sample of men and women attending the sexual health clinic between September 1, 2013, and December 20, 2013.
Interventions Participants underwent testing for M genitalium, along with standard sexually transmitted infection screening. All samples that had positive results for M genitalium were tested for mutations associated with resistance to macrolides and fluoroquinolones. Mycoplasma genitalium treatment was based on resistance profile and verified with a test of cure.
Main outcome measures Positive results for M genitalium and antibiotic resistance.
Results A total of 1193 men and women participated in the study. Overall, 4.5% of the 884 men and 3.2% of the 309 women had positive test results for M genitalium. Asymptomatic infection was common (52.0%). Macrolide resistance–mediating mutations were found in 58.0% of the M genitalium infections. No treatment failure was observed for azithromycin-treated cases. Treatment failure was suspected for 16.7% of cases treated with moxifloxacin.
Conclusion Mycoplasma genitalium is present in Canada, with a prevalence comparable to chlamydia and gonorrhea, and has high macrolide and fluoroquinolone resistance.
Mycoplasma genitalium is an emerging sexually transmitted infection (STI). The bacterium has been identified as the causative organism of 10% to 25% of all nongonococcal urethritis (NGU) in men and women,1 and 2% to 4.5% of asymptomatic NGU cases.2,3 Clinical presentation is similar to Chlamydia trachomatis and Neisseria gonorrhoeae.1,2 Mycoplasma genitalium has been detected in the urethra, vagina, and rectum, locations that allow infection to spread via vaginal and anal sex.4
The complications of M genitalium infection are not fully understood, but infection is suspected to have the same sequelae as infection with C trachomatis, including pelvic inflammatory disease, infertility, epididymitis, and increased risk of HIV infection.1,5 Recent treatment effectiveness studies have demonstrated the emergence of drug resistance in M genitalium to antibiotics commonly used to treat NGU.6–8
The purpose of our study was to estimate the prevalence of M genitalium in Toronto, Ont, assess rates of antimicrobial resistance, and describe treatment outcomes to inform clinical practice.
METHODS
Study design
A prospective and consecutive sample of male, female, and transgender clients seeking sexual health services at the Men/Trans Clinic and Women/Trans Clinic at the Hassle Free Clinic in Toronto between September 1, 2013, and December 20, 2013 was included in the study, regardless of age. Clients could opt out of the study if they did not want to participate or if they did not want to receive M genitalium testing. Clients who opted out still received standard STI testing. Our target sample size was 1000 participants.
Biological sampling
Participants provided a first-void urine sample for STI testing. We used urine to test for M genitalium to reduce differential bias between male and female participants and to minimize clinic work. The test for M genitalium was added as a separate test in the panel. Biological samples were transported to the Public Health Ontario Laboratory with existing daily shipments for laboratory analysis.
Laboratory analysis
A sample of 1800 μL of urine was centrifuged at 20 000 g for 15 minutes, and the pellet was resuspended in 300 μL of 20% (weight/volume) ion exchange resin (Chelex 100) slurry in Tris-EDTA buffer. The mixture was vortexed for 60 seconds and incubated at 95°C for 10 minutes. After centrifugation at 20 000 g for 5 minutes, 5 μL of the supernatant was analyzed using real-time polymerase chain reaction (PCR) targeting the gene MgPa.9 Proficiency testing was provided by the Statens Serum Institut in Copenhagen, Denmark, to confirm the test performance within the Public Health Ontario Laboratory. Confirmation of positive samples was performed by real-time PCR using an M genitalium–specific 23S target developed at the Public Health Ontario Laboratory.9 Samples were considered indeterminate if they had a negative confirmatory PCR result.
All specimens with positive test results for M genitalium were analyzed for macrolide resistance–mediating mutations in region V on the 23S rRNA gene by PCR assay,10 and for mutations associated with fluoroquinolone resistance in parC and gyrA.6
Specimen processing occurred 2 to 5 times per week at the Public Health Ontario Laboratory, depending on sample submission volume, with the test results being communicated back to the clinic within approximately 24 hours. All participants who had positive test results for M genitalium were contacted for appropriate follow-up and treatment. Sexual contacts of those who had positive results were tested and treated as necessary.
Treatment of M genitalium
Azithromycin (500 mg on day 1, followed by 250 mg per day for 4 days) was the first-line treatment recommended for those with positive results for M genitalium. Cases identified as carriers of a strain with a macrolide resistance–mediating mutation were treated with moxifloxacin (400 mg daily for 7 days). Patients were asked to return to the clinic 2 to 4 weeks after treatment to undergo a test of cure (TOC). A repeat positive M genitalium PCR test result at the TOC was considered a treatment failure, and moxifloxacin was used to treat these infections even if no azithromycin mutations were detected.
We documented and monitored treatment outcomes to develop best-practice recommendations for uncomplicated (no co-infection, no antibiotic resistance) and complicated (co-infection or antibiotic resistance) M genitalium infection. The University of Toronto Research Ethics Board approved this study.
RESULTS
A total of 1193 clinic attendees participated in the study. Participants ranged in age from 19 to 57 years (mean 33 years) and most were men (74.1%).
Prevalence of M genitalium
The overall prevalence of M genitalium was 4.2% (95% CI 3.2% to 5.5%; Table 1). The prevalence of M genitalium was higher for men (4.5%, 95% CI 3.3% to 6.1%) than women (3.2%, 95% CI 1.6% to 5.9%); however, it was not significantly higher (P = .33). The prevalence of C trachomatis was 5.2% (95% CI 4.0% to 6.6%) and the prevalence of N gonorrhoeae was 4.4% (95% CI 3.3% to 5.7%). The M genitalium co-infection rate was 12.0% (Table 1). Half of the men and 60.0% of the women infected with M genitalium reported no symptoms. Most of the asymptomatic infections were identified during routine STI testing for men and routine STI testing and physical examinations for women.
Estimated Mycoplasma genitalium prevalence, including key characteristics and co-infections
Macrolide and fluoroquinolone resistance
Macrolide resistance–mediating mutations were detected in 29 of the 50 patients (58.0%) with positive results for M genitalium (included mutations A2058G and A2059G). Among men, 25 (62.5%) carried macrolide-resistant strains and 13 (52.0%) were symptomatic. Among women, 4 (40.0%) carried macrolide-resistant strains and 3 (75.0%) were symptomatic. Ten individuals (20.0%) harboured strains with the parC mutations previously associated with resistance to moxifloxacin6 (G248T and G259A). No mutations in gyrA were identified.
Treatment outcomes
All 50 participants who had positive test results for M genitalium were offered treatment, of whom 43 accepted (Figure 1). Seven declined treatment of M genitalium or indicated they would seek treatment with another doctor.
Flowchart of the treatment outcomes of patients with positive test results for Mycoplasma genitalium in Toronto, Ont, in 2013
TOC—test of cure.
*A total of 11 patients initially received doxycycline based on symptoms, and were subsequently switched to either azithromycin or moxifloxacin, with the exception of 3 who had negative TOC results after treatment with doxycycline.
†There were 3 potential treatment failures in those taking moxifloxacin (2 had resolved symptoms).
Following standard practice, all symptomatic NGU cases were treated with doxycycline at the time of presentation (Figure 1). Symptomatic NGU patients with positive test results for M genitalium were subsequently switched to either azithromycin or moxifloxacin depending on their macrolide-resistance profile. Eleven men were treated with doxycycline owing to symptoms. Three of these men (27.3%) were successfully treated with doxycycline, had negative TOC results for M genitalium, and did not require further treatment. The remaining 8 men had positive TOC results for M genitalium and were switched to appropriate M genitalium treatment (either moxifloxacin or azithromycin). No women were given doxycycline as an initial treatment, and all were treated with azithromycin from the outset.
Azithromycin (total dose of 1.5 g) was administered to 12 men and 6 women (Figure 1). Overall, 15 of the 18 patients treated with azithromycin had negative TOC results for M genitalium and 3 were lost to follow-up.
Moxifloxacin was administered to 18 men and 4 women (Figure 1). Four were lost to follow-up and 18 underwent TOCs. Of these, 11 (61.1%) had negative TOC results for M genitalium and 3 (16.7%) had positive TOC results for M genitalium, after the recommended 2- to 4-week wait period and self-reported abstinence from sexual intercourse, although these results would be more certain if they had waited 4 to 6 weeks after treatment. Of the 3 patients with positive TOC results, 2 continued to have positive test results with no evidence of clearing the infection.
Three co-infected patients were successfully treated with moxifloxacin and 1 co-infected patient was successfully treated with doxycycline. Two co-infected patients were lost to follow-up.
DISCUSSION
Mycoplasma genitalium is present in Toronto. The prevalence of M genitalium was comparable to the prevalence of C trachomatis and N gonorrhoeae, although our prevalence is likely underestimated, as the relative sensitivity of M genitalium detection is only 61% for urine samples.4 Resistance to macrolide (58.0%) and fluoroquinolone (20.0%) treatment was high and comparable to the resistance observed in other studies.7
Macrolide and fluoroquinolone resistance poses an important clinical challenge to treating both M genitalium and NGU. Azithromycin (1 g or extended dose [500 mg on day 1, followed by 250 mg per day for 4 days]) has been the preferred first-line treatment of M genitalium, and moxifloxacin has been recommended as a second-line treatment when treatment failures are observed.11 Doxycycline is not a viable first-line option, given rates of clinical cure as low as 17.1%.8
Currently, the Canadian Guidelines on Sexually Transmitted Infections recommend treating NGU with 1 week of doxycycline (100 mg twice a day) or a single dose of azithromycin (1 g).12 This treatment schedule might not be sufficient to eradicate M genitalium NGU, leading to treatment failure, persistent NGU, and potential development of macrolide resistance.
Mycoplasma genitalium infection is a common cause of persistent NGU, especially if doxycycline or azithromycin treatment failure is observed. In this situation, moxifloxacin should be considered, in particular if azithromycin was used as the initial treatment. Given the high level of macrolide resistance in this population, second-line treatment with azithromycin after doxycycline might not be an optimal solution unless macrolide susceptibility has been documented.
Moxifloxacin treatment failure was observed in our study and the patients treated with moxifloxacin were already carrying macrolide-resistant strains. Tested treatment options for such multidrug-resistant strains are currently lacking. Doxycycline is likely to be effective in less than 30% of these cases, and for the remaining, new treatment options are urgently needed. Fluoroquinolone resistance and failure after moxifloxacin treatment has been reported recently7 and seems to be increasing. The rise of M genitalium resistance to commonly used therapies in the treatment of NGU emphasizes the need to specifically identify M genitalium and treat it appropriately to avoid perpetuating resistance.
Conclusion
Our study provides evidence that M genitalium is present in Canada. The prevalence of M genitalium will be lower in the general population than it is for the high-risk population in this study. At the same time, prevalence comparable to C trachomatis and N gonorrhoeae and high resistance to first-line treatment recommendations suggest this emerging STI could rapidly become more prevalent and difficult to treat. These results underscore the need to better care for and educate patients in transmission prevention. Future studies should collect information on epidemiologic risk factors and co-infection status to assist with this endeavour.
Acknowledgments
We thank the Hassle Free Clinic and Public Health Ontario Laboratory for making this study happen. Specifically, we thank Public Health Ontario Laboratory for developing and validating the Mycoplasma genitalium diagnostic test used for this study, and the Hassle Free Clinic for incorporating this study into their work flow and covering the associated added costs of treatment. This study was funded by Public Health Ontario, the Hassle Free Clinic, and the University of Toronto.
Notes
EDITOR’S KEY POINTS
The prevalence of Mycoplasma genitalium in this study was 4.2% (95% CI 3.2% to 5.5%), which was comparable to the prevalences of Chlamydia trachomatis (5.2%, 95% CI 4.0% to 6.6%) and Neisseria gonorrhoeae (4.4%, 95% CI 3.3% to 5.7%).
Resistance to macrolide (58.0%) and fluoroquinolone (20.0%) treatment was high, which suggests this emerging sexually transmitted infection could rapidly become more prevalent and difficult to treat.
Moxifloxacin treatment failure was observed and the patients treated with moxifloxacin were already carrying macrolide-resistant strains. Tested treatment options for such multidrug-resistant strains are currently lacking. Doxycycline is likely to be effective in less than 30% of these cases, and for the remaining, new treatment options are urgently needed.
POINTS DE REPÈRE DU RÉDACTEUR
Dans cette étude, la prévalence du Mycoplasma genitalium était de 4,3 % (IC à 95 % 3,2 % à 5,5 %), ce qui est comparable aux prévalences de la Chlamydia Trachomatis (5,2 %, IC à 95 % 4,0 % à 6,6 %) et du Neisseria gonorrheae (4,4 %, IC à 95 % 3,3 % à 5,7 %).
La résistance aux macrolides et aux fluoroquinolones était élevée (20 %), ce qui suggère que la prévalence de cette nouvelle infection à transmission sexuelle risque d’augmenter et d’être difficile à traiter.
Chez des patients déjà porteurs d’une souche résistante aux macrolides, la moxifloxacine s’est avérée inefficace. Actuellement, il n’existe pas d’option de traitement ayant fait ses preuves pour ces souches résistantes à plusieurs antibiotiques. La doxycycline est susceptible d’être efficace dans moins de 30 % de ces cas, et pour le reste, il faudra de toute urgence de nouvelles options de traitement.
Footnotes
This article has been peer reviewed.
Cet article a fait l’objet d’une révision par des pairs.
Contributors
Dr Gesink contributed to the conception of the work; all authors contributed to the design of the work. Dr Allen, Mr Mitterni, Dr Juzkiw, Ms Jamieson, Ms Racey, Ms Seah, Dr Zittermann, Mr Singh, and Dr Jensen contributed to the acquisition of the data for the work. Dr Allen and Ms Racey contributed to the analysis of the data; all authors contributed to the interpretation of the results; and all authors were involved in drafting, critically reviewing, revising, and approving the manuscript. All authors are accountable for all aspects of the work, its accuracy, and its integrity.
Competing interests
None declared
- Copyright© the College of Family Physicians of Canada