Treatment efficacy, treatment failures and selection of macrolide resistance in patients with high load of Mycoplasma genitalium during treatment of male urethritis with josamycin

Background Azithromycin has been widely used for Mycoplasma genitalium treatment internationally. However, the eradication efficacy has substantially declined recent decade. In Russia, josamycin (another macrolide) is the recommended first-line treatment for M. genitalium infections, however, no data regarding treatment efficacy with josamycin and resistance in M. genitalium infections have been internationally published. We examined the M. genitalium prevalence in males attending an STI clinic in Moscow, Russia from December 2006 to January 2008, investigated treatment efficacy with josamycin in male urethritis, and monitored the M. genitalium DNA eradication dynamics and selection of macrolide resistance in M. genitalium during this treatment. Methods Microscopy and real-time PCRs were used to diagnose urethritis and non-viral STIs, respectively, in males (n = 320). M. genitalium positive patients were treated with recommended josamycin regimen and treatment efficacy was monitored using quantitative real-time PCR. Macrolide resistance mutations were identified using sequencing of the 23S rRNA gene. Results Forty-seven (14.7%) males were positive for M. genitalium only and most (85.1%) of these had symptoms and signs of urethritis. Forty-six (97.9%) males agreed to participate in the treatment efficacy monitoring. All the pre-treatment M. genitalium specimens had wild-type 23S rRNA. The elimination of M. genitalium DNA was substantially faster in patients with lower pre-treatment M. genitalium load, and the total eradication rate was 43/46 (93.5%). Of the six patients with high pre-treatment M. genitalium load, three (50%) remained positive post-treatment and these positive specimens contained macrolide resistance mutations in the 23S rRNA gene, i.e., A2059G (n = 2) and A2062G (n = 1). Conclusions M. genitalium was a frequent cause of male urethritis in Moscow, Russia. The pre-treatment M. genitalium load might be an effective predictor of eradication efficacy with macrolides (and possibly additional antimicrobials) and selection of macrolide resistance. Additional in vivo and in vitro data are crucial to support the recommendation of using josamycin as first-line treatment for M. genitalium infections in Russia. It would be valuable to develop international M. genitalium management guidelines, and quantitative diagnostic PCRs determining also M. genitalium load and resistance mutations (for macrolides and ideally also moxifloxacin) should ideally be recommended.

Still, no international management guidelines for M. genitalium infections have been published. The recommended treatments of male NGU in the European guideline include tetracyclines and macrolides [9]. However, despite being effective in vitro tetracyclines have shown a low eradication rate for M. genitalium clinically [1,[10][11][12][13]. Azithromycin 1 g single oral dose has been widely used. However, despite that large, appropriate randomized clinical trials are lacking an extended azithromycin regimen has been indicated to be slightly more effective or at least equally effective in eradicating M. genitalium, i.e., azithromycin 500 mg on day 1 followed by 250 mg daily on days 2-5 [1,11,[13][14][15]. Worryingly, the eradication rate of M. genitalium after azithromycin 1 g therapy has substantially declined during the last decade [1,10,[12][13][14]16]. Recently, it was also reported that azithromycin 1 g therapy was associated with selection of azithromycin resistance in M. genitalium [14]. It was also most recently hypothesized that treatment failure can be associated with a higher load of M. genitalium in the clinical specimens [17]. M. genitalium strains resistant to azithromycin contain resistance mutations in region V of 23S rRNA, which is encoded be a single copy gene in M. genitalium [1,10,13,14,18]. Moxifloxacin is the most commonly used second-line regimen in patients failing azithromycin therapy. However, the side-effects, cost, and the risk of selection of resistance limit the moxifloxacin use [1,13,15,19,20].
In Russia, the 16-membered lactone ring macrolide josamycin (500 mg three times daily, 10 days) is the nationally recommended first-line treatment for M. genitalium infections and it is widely used mainly in the treatment of NGU, C. trachomatis infections and M. genitalium infections, including in pregnancy [21]. Josamycin is also included in the second-line treatment in the European C. trachomatis management guideline [22], however, in general josamycin is very rarely used in the majority of European countries. Despite that the in vitro susceptibility to josamycin in M. hominis and ureaplasmas are high [23,24], very limited in vitro data regarding josamycin susceptibility in M. genitalium have been published [25], which have not indicated a higher activity than azithromycin. Furthermore, no data regarding treatment efficacy of M. genitalium infections with josamycin have been published in the international (English language) literature. Moxifloxacin 400 mg daily, 10 days can be used as a second-line regimen for treatment of M. genitalium infections in Russia.
The aims of this study were to examine the prevalence of M. genitalium in males attending an STI clinic in Moscow, Russia from December 2006 to January 2008, investigate the treatment efficacy with josamycin in male urethritis, and to monitor the M. genitalium DNA eradication dynamics and selection of macrolide resistance in M. genitalium during treatment of male urethritis with josamycin.

Methods
The work was performed at the Department of Molecular Diagnostics and Epidemiology, Central Research Institute for Epidemiology, Moscow, Russia.

Study population
Consecutive males (n = 320) attending one of the venereologist at a sexually transmitted infection (STI) clinic in Moscow, Russia, from December 2006 to January 2008, were enrolled in the study. The males attended the STI clinic due to urethral symptoms or having had unprotected sexual intercourse with new or multiple contact(s). The mean age of the males was 31 years (median age: 30 years; range: 18 to 66 years). All males signed an informed consent form, the males were clinically examined and two urethral swabs were sampled from each patient, i.e. for microscopy and PCR, respectively.

Ethical approval
Ethical approval for the study was obtained by the Central Research Institute for Epidemiology, Moscow, Russia.

Laboratory diagnostics (microscopy and PCR)
Microscopy (1000× magnification) of Gram-stained smears was performed. The presence of ≥5 polymorphonuclear leucocytes (PMNL) per high power field (hpf), in at least 5 hpf, was interpreted as urethritis. For diagnosis, M. genitalium DNA was detected by the real-time PCR assay AmpliSens® M.genitalium-FRT, and the AmpliSens® N.gonorrhoeae-FRT, AmpliSens® C.trachomatis-FRT, and AmpliSens® T.vaginalis-FRT assays (InterLabServices Ltd, Moscow, Russia) were used to diagnose other non-viral STIs. The DNA isolation and PCR assays, which have been previously evaluated, were performed in accordance with the instructions from the manufacturer (InterLabServices Ltd, Moscow, Russia) and as previously described [26][27][28][29].

Antimicrobial treatment of patients
In accordance with the Russian treatment guidelines, all M. genitalium positive patients were treated with josamycin 500 mg three times daily, 10 days [21]. Treatment failures with the josamycin regimen were administered moxifloxacin 400 mg daily, 10 days. Patients positive for any other STI (according to the laboratory test results) were also treated in accordance with the Russian treatment guidelines [21].

Monitoring of josamycin treatment efficacy
All M. genitalium positive patients that did not have any other STI, any complicated urogenital infection, or had been administered any antimicrobials in four weeks prior to enrollment, were invited for monitoring of treatment efficacy. In participating patients, one urethral swab (for microscopy) and one first-void urine specimen (for PCR) were sampled, in a standardized and quality assured manner, on treatment onset, 3rd and 8th day of treatment, and 2nd and 14th days after completed treatment. The first-void urine was collected in 50 mL sterile disposable plastic containers, with a calibration scale in mL on the wall of the container. According to instructions and using these containers, the patients collected 15-20 mL of first-void urine (predominantly morning urine and the patients should not had urinated 3 h before). Valid data regarding the time since last micturition was unfortunately not possible to obtain. At each visit, compliance of the therapy was ensured. To quantify the M. genitalium load in these clinical specimens, three in house prepared DNA calibrators based on the gyrB gene (10 2 , 10 3 , 10 4 genome equivalents (geq)/reaction) were included in the real-time PCR assay AmpliSens® M.genitalium-FRT (InterLabService Ltd, Moscow, Russia) [26]. The M. genitalium concentration detected was expressed as number of geq [log 10 ] per 1 mL of transport media and the M. genitalium load in each specimen was arbitrarily categorized as low (≤4 geq/mL [log 10 ]), moderate (>4 -<6 geq/mL [log 10 ]) or high (≥6 geq/mL [log 10 ]). The M. genitalium positive samples were subsequently preserved at −70°C, that is, prior to sequencing for identification of macrolide resistance mutations.

Identification of macrolide resistance mutations
For identification of macrolide resistance mutations, domain V of the 23S rRNA gene in M. genitalium was sequenced using the previously described primers Mg23S-1992F and Mg23S-2138R [18].

Mycoplasma genitalium positive males
In total, M. genitalium was detected in 51 (15.9%) of the 320 includes males. However, four of the M. genitalium positive males were also positive for some additional STI etiological agent, that is, C. trachomatis (n = 2), T. vaginalis (n = 1), and Herpes simplex virus type 2 (n = 1). For the treatment monitoring, these four males were excluded. However, no males were excluded due to having a complicated urogenital infection or taking antimicrobials during the four weeks prior to enrollment. Accordingly, For example, all the 13 (100%) patients with low pre-treatment bacterial load were M. genitalium negative already after three days of treatment, and only 6.9% (2/29) of patients with moderate pretreatment M. genitalium load had detectable levels of M. genitalium DNA two days post-treatment, which was eliminated 10-14 days post-treatment. However, of the six patients with high pre-treatment M. genitalium load three (50%) remained positive 10-14 days after completed treatment ( Table 2). All these three patients repeatedly assured full compliance to treatment and not having had any sexual contacts between initiation of josamycin therapy and follow up visit 10-14 days after completed treatment. Accordingly, the eradication rate with the josamycin treatment was 43/46 (93.5%). Details regarding the three treatment failures are provided in Table 3.

Treatment failures with josamycin (n = 3)
Briefly, at the time of diagnosis two of the three patients had severe symptoms of urethritis and high number of PMNL/hpf, however, the remaining patient was asymptomatic with <5 PMNL/hpf. In the two symptomatic patients, the symptoms and signs initially resolved. However, one of them had relapsed symptoms and signs of severe urethritis 10-14 days after treatment, which was also the case for the initially asymptomatic patient. The M. genitalium strains in all three patients had mutations in the macrolide resistance region of 23S rRNA during treatment. Accordingly, the M. genitalium strains in two and one of those patients had an A2059G mutation (Escherichia coli numbering) and A2062G mutation, respectively, in the 23S rRNA gene ( Table 3). The patients were subsequently successfully treated with moxifloxacin 400 mg daily, 10 days.

Discussion
In the present study, it was shown that M. genitalium is a frequent cause of male urethritis in Moscow, Russia and that the M. genitalium eradication rate in 2006-2008 was 93.5% with the recommended first-line treatment in Russia, that is, josamycin 500 mg three times daily, 10 days [21]. These are the first data published regarding efficacy using josamycin for treatment of M. genitalium infections in the international (English language) literature. Accordingly, no evidence-based data supporting josamycin, compared to e.g. azithromycin, for treatment of M. genitalium infections and exceedingly limited in vitro data regarding josamycin susceptibility in M. genitalium, have been internationally published. To our best knowledge, the only in vitro antimicrobial susceptibility data were published in 1992 (only seven isolates were tested) and the activity was slightly lower compared to azithromycin [25]. In the present study, it was also shown that josamycin resistance resulting in treatment failures can rapidly be selected during treatment. The eradication rate of M. genitalium after the internationally widely used azithromycin 1 g therapy has substantially declined during the last decade [1,10,[12][13][14]16]. Treatment with azithromycin 1 g was also recently associated with selection of macrolide resistant M. genitalium [14], and it was also hypothesized that treatment failures are frequently associated with a higher load of M. genitalium [17]. The results of the present study, instead examining the macrolide josamycin, are in full concordance with these recent findings. Accordingly, three failures to treat male M. genitalium urethritis with josamycin were verified. All of these patients had a high pre-treatment M. genitalium load (>6 geq/mL [log 10 ]) and M. genitalium cells with mutations in the macrolide resistance-determining region V of 23S rRNA [1,10,13,14,18] were selected during treatment. Thus, despite that no 23S rRNA gene mutations were identified in the pre-treatment M. genitalium specimens the term selected resistance instead of induced resistance was used in the present study. Accordingly, it was considered that an undetected minority population of macrolide resistant M. genitalium cells might have been present already pre-treatment. These resistant cells, in the specimens with high M. genitalium load, could subsequently be selected during treatment with the bacteriostatic josamycin. The probability of this selection scenario was considered higher particularly because it is unknown how frequently josamycin might be able to directly induce 23S rRNA gene mutations, especially during treatment of M. genitalium with a very long generation time. The three identified treatment failures were further supported by the rebound in M. genitalium loads in all three patients and the recrudescence of symptoms in two of the three patients. Thus, the pre-treatment M. genitalium load might be an effective predictor of eradication efficacy with macrolides (and possibly additional antimicrobials) and selection of macrolide resistance due to mutations in the 23S rRNA gene. Unambiguously, additional data are crucial to support the recommendation of using josamycin regimen as first-line treatment in the Russian treatment guidelines for M. genitalium infections. The most frequent 23S rRNA mutations identified in M. genitalium strains resistant to the 15-membered macrolide azithromycin have been A2058G and A2059G [1,13,14,17,18,30,31]. In the present study, it was for the first time shown that the A2059G mutation is associated also with M. genitalium resistance to 16-membered macrolides, e.g. josamycin. It has been earlier demonstrated that the A2059G mutation results in high-level resistance to 16-membered macrolides in the closely related species M. pneumoniae [32]. The A2062G mutation found in the remaining treatment failure has not been previously described in M. genitalium. However, M. hominis and M. pneumoniae cells with A2062G and A2062T mutations in the 23S rRNA gene have been previously selected in vitro using josamycin and shown to cause high-level josamycin resistance [33,34]. Interestingly, previous studies have suggested that mutations in the A2062 position of the 23S rRNA gene result in resistance to the 16-membered macrolides (e.g., josamycin), but not necessarily to the 15-membered macrolides (e.g., azithromycin), indicating a slightly different binding site [35][36][37]. All three patients repeatedly reassured that they had not had any unprotected sexual contacts between initiation of the josamycin treatment and test of cure. All patients were subsequently successfully treated with moxifloxacin 400 mg single oral dose daily in 10 days, which was confirmed by lack of symptoms, signs and M. genitalium DNA at follow up visit four weeks after the treatment.
In M. pneumoniae, the A2062G mutation, detected after in vitro exposure of josamycin, has also been shown to significantly increase the MICs of the streptogramin pristinamycin [34]. This is of grave concern because pristinamycin is highly active against M. genitalium infections and currently the only treatment option for infections resistant to both azithromycin and moxifloxacin [38]. Nevertheless, it remains unknown if an A2058G/A2059G mutation (resulting in azithromycin resistance) and an A2062G mutation (resulting in resistance to pristinamycin (and josamycin)) can co-exist in the 23S rRNA gene of M. genitalium, i.e. without severely decreasing the biological fitness and possibilities for transmission of the M. genitalium strain.

Conclusions
In the present study, it was shown that M. genitalium is a frequent cause of male urethritis in Moscow, Russia. Furthermore, the first data on efficacy using josamycin for treatment of M. genitalium urethritis were also presented (93.5% eradication rate). All the three verified treatment failures had a high pre-treatment M. genitalium load and cells with mutations in the macrolide resistance region of 23S rRNA were easily selected during treatment. Because the present study examined material from December 2006 to January 2008 and the population selective pressure for resistance due to wide usage of macrolides has been very large and selected for relatively high-levels of azithromycin resistance in many countries during the recent decade, it is crucial to examine the josamycin treatment efficacy and M. genitalium load, including cut-off for possible treatment failure, as well as to screen for resistance to macrolides (and other antimicrobials) in a more recent material of M. genitalium positive clinical specimens (pre-and post-treatment) in Russia. This should ideally include both genetic screening for macrolide resistance mutations (previously described and novel), moxifloxacin resistance mutations and culture of M. genitalium, including MIC determination for macrolides (including azithromycin and josamycin), moxifloxacin and pristinamycin to confirm the phenotypic effects of the mutations on the antimicrobial resistance. No evidence-based data supporting josamycin, compared to e.g. azithromycin, for treatment of M. genitalium infections and exceedingly limited in vitro data regarding josamycin susceptibility in M. genitalium, have been internationally published [25]. Accordingly, additional in vivo and in vitro data are crucial to support the currently recommended josamycin regimen as first-line treatment in the Russian treatment guidelines for M. genitalium infections. It would be valuable to develop and implement international guidelines for management of M. genitalium infections and the results of the present study indicate that quantitative diagnostic PCRs determining also M. genitalium load and resistance mutations (for macrolides and ideally also moxifloxacin) should ideally be recommended for diagnosis of M. genitalium infections. Finally, novel options for effective treatment of M. genitalium infections are essential and dual antimicrobial therapy, which has been introduced for gonorrhoea, might need to be considered also for M. genitalium infections.