The primary pathogens of non-gonococcal urethritis (NGU) are *Chlamydia trachomatis* and *Mycoplasma genitalium*. The symptoms of chlamydial urethritis and *M genitalium*-related urethritis are quite similar, and patients with NGU have been treated upon their first visit to clinics without knowledge of the specific pathogens underlying their conditions. In any guidelines, either azithromycin or doxycycline regimens are recommended for NGU.[@b1] [@b2] However, previous studies have demonstrated that doxycycline shows poor efficacy against *M genitalium*-related urethritis,[@b3] whereas the eradication rates of azithromycin against *M genitalium* were approximately 80%.[@b4] Fluoroquinolones show good antichlamydial activity, much like tetracycline and macrolides. The ability of moxifloxacin to eradicate azithromycin-resistant *M genitalium* at a lower minimum inhibitory concentration (MIC) has previously been demonstrated,[@b4; @b5; @b6] but levofloxacin shows a poor activity.[@b7]

Gatifloxacin is an 8-methoxy fluoroquinolone that shows a broad spectrum and increased antibacterial activities against Gram-positive cocci bacteria, anaerobes, chlamydias and mycoplasmas.[@b8] The antimicrobial activity of gatifloxacin against *M genitalium* has been shown to be intermediate between those of moxifloxacin and levofloxacin.[@b6] As gatifloxacin also showed good activities against *C trachomatis*, it could be used as a potential treatment regimen for male NGU; thus, we started an open clinical trial evaluating the effectiveness of gatifloxacin in the treatment of NGU. Unfortunately, gatifloxacin was removed from the US Food and Drug Administration-approved drug list in September 2008 due to serious side effects including abnormal blood glucose levels.[@b9] The US Food and Drug Administration determination ultimately prevented us from completing this study. Regardless of this, it was decided that this paper would be published because gatifloxacin was an available treatment for NGU at the time it was initiated, and our data provide a potentially useful insight into the treatment of *M genitalium*-related urethritis.

Materials and methods
=====================

Patients
--------

Male outpatients more than 20 years old, who had symptoms of urethritis including pus discharge, micturation pain, urethral discomfort and itching, were recruited for this study. Patients gave their written consent and agreed to refrain from sexual activity without condoms between their first and last visits. Patients were excluded from the study if they had diabetes mellitus, displayed an allergy to gatifloxacin, were infected with *Neisseria gonorrhoeae*, were intolerant to gatifloxacin, required therapy with other antimicrobial agents, had severe dysfunction of the heart or liver, were treated with gatifloxacin within the 7 days before the first visit and whose symptoms of urethritis were improving or who had either a history of or diseases relating to epilepsy. The clinicians confirmed the selection and exclusion criteria of the patients for this study and enrolled patients to a specified non-profit corporation, the Supporting Center for Clinical Research and Education, Osaka, Japan, by fax. This study was approved by the ethics committee of Osaka University, Osaka, Japan.

Procedures
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Patients with NGU were given a 200 mg dose of gatifloxacin twice a day for 7 days. On the first visit by patients, clinical symptoms were recorded, the first voided urine of patient was analysed and urine specimens for microbiological examination were collected. Patients with less than five white blood cells (WBC) per high power field in the urinary sediments or 10 WBC/μl of uncentrifuged urine specimens were omitted. Patients re-visited the clinic for evaluation 2--3 weeks after gatifloxacin treatment and the same procedures as the first visit were performed. Finally, the efficacy of gatifloxacin was evaluated microbiologically and the clinical cure rates determined at the re-visit.

Urine collection and microbiological examinations are described below. Approximately 20--30 ml of first voided urine was collected from each patient at least 1 h after their latest urination. A total of 2 ml from these specimens was used for the detection of *C trachomatis* and *N gonorrhoeae* using the Aptima Combo2 assay (SRL Co. Ltd., Tokyo, Japan). Then, 8 ml was stored in a freezer until analysis for *M genitalium* and the rest was discarded. Analysis for *M genitalium* was performed at the laboratory of urology, Faculty of Medicine, Miyazaki University, Japan. *M genitalium* was screened by using a real-time PCR assay (TaqMan assay) as described by Jensen *et al*.[@b10] Specimens with positive results were re-analysed using a 16S ribosomal RNA PCR assay for confirmation.

Results
=======

Between March and September 2008, 169 male patients were enrolled in this study. Among these patients, nine who had had sexual intercourse without a condom during the study period, 22 who did not participate in follow-up visits, two who used other antimicrobial agents and one with an adverse effect (diarrhoea) were omitted. Finally, microbiological and clinical cure rates could be evaluated in 86 patients detected with *C trachomatis* or *M genitalium* and in 135 with NGU, respectively.

In 135 patients with NGU, *C trachomatis* and *M genitalium* were detected from 53% and 13%, respectively ([table 1](#tbl1){ref-type="table"}). Microbiological cure rates against *C trachomatis* and *M genitalium* were 100% and 83%. *M genitalium* remained in three patients, but clinical symptoms were cured with or without the eradication of *M genitalium*. Micturition pain and urethral itching remained in two with chlamydial urethritis after the eradication of *C trachomatis*. The total clinical cure rate was 99%.

###### 

Microbiological and clinical outcome of gatifloxacin against NGU

  Urethritis             Pathogens   N       Microbiological outcomes (n=86)   Clinical outcomes (n=135)                           
  ---------------------- ----------- ------- --------------------------------- --------------------------- ------- ------- ------- -------
  CU                     CT          68      68/68                             --                          42/42   33/33   45/46   33/34
  CT+MG                  4           4/4     4/4                               2/2                         3/3     2/2     1/1     
  NCNGU                  MG          14      --                                11/14                       12/12   9/9     7/7     7/7
  Not detected           48          --      --                                33/33                       21/21   33/33   23/23   
  Indeterminate for CT   1           --      --                                1/1                         --      1/1     1/1     
  Total                  135         72/72   15/18                             91/91                       66/66   90/91   65/66   

CT, *C trachomatis*; CU, chlamydial urethritis; MG, *M genitalium*; NCNGU, non-chlamydial non-gonococcal urethritis; NGU, non-gonococcal urethritis.

Discussion
==========

The effectiveness of fluoroquinolones against *M genitalium*-related urethritis is varied. Of the fluoroquinolone compounds tested, the MIC90 values of moxifloxacin, sitafloxacin, gatifloxacin, levofloxacin, ciprofloxacin and norfloxacin were 0.125 μg/ml, 0.125 μg/ml, 0.25 μg/ml, 2 μg/ml, 8 μg/ml and 64 μg/ml, respectively.[@b6] Of these fluoroquinolones, moxifloxacin, gatifloxacin and levofloxacin were studied clinically, and their microbiological efficacies were 100%,[@b4] 83% and 25%,[@b7] respectively. Assuming that fluoroquinolone tissue levels are equivalent for all drugs in this class, an MIC90 of 0.125 μg/ml or less may be necessary for optimal activity against *M genitalium*. These data may be useful in selecting new fluoroquinolones for clinical treatment trials in men with NGU, specifically for the treatment of *M genitalium*. Moxifloxacin is currently not recommended by any of the various sexually transmitted infection treatment guidelines for this purpose and should be studied further in order to be accorded such a recommendation.

In three patients, *M genitalium* was not eradicated. The *M genitalium* DNA loads increased after treatment in only one case (793--275 369 geq). On the last visit, this patient showed no signs of urethral discharge, although the WBC in the urinary sediments remained. In two cases, the *M genitalium* DNA loads decreased (23 373--11 geq, 167020--10 geq), but these specimens were still positive for *M genitalium* by 16S rRNA PCR assay.

**Funding:** This study received funding from the Supporting Center for Clinical Research and Education (SCCRE), Osaka, Japan.

**Competing interests:** None declared.

**Patient consent:** Obtained.

**Ethics approval:** This study was conducted with the approval of the ethics committee of Osaka University, Osaka, Japan.

**Contributors:** RH initiated the study, collected samples and was responsible for analysis of samples for *M genitalium*, participated in data analysis and wrote the first draft of the manuscript. ST, HK, MY, HH and SA participated in planning the study, collected samples and edited the manuscript. KT was a deputy of a specified non-profit corporation, the Supporting Center for Clinical Research and Education, Japan for enrolling patients. TM initiated the study, is a deputy of the study group and edited the manuscript.

**Provenance and peer review:** Not commissioned; externally peer reviewed.
