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  <front>
    <journal-meta>
      <journal-id journal-id-type="publisher-id">87</journal-id>
      <journal-id journal-id-type="index">urn:lsid:arphahub.com:pub:A116C711-4C18-5A38-8F1E-5E97753A8A64</journal-id>
      <journal-title-group>
        <journal-title xml:lang="en">Folia Medica</journal-title>
        <abbrev-journal-title xml:lang="en">FM</abbrev-journal-title>
      </journal-title-group>
      <issn pub-type="ppub">0204-8043</issn>
      <issn pub-type="epub">1314-2143</issn>
      <publisher>
        <publisher-name>Plovdiv Medical University</publisher-name>
      </publisher>
    </journal-meta>
    <article-meta>
      <article-id pub-id-type="doi">10.3897/folmed.64.e63624</article-id>
      <article-id pub-id-type="publisher-id">63624</article-id>
      <article-categories>
        <subj-group subj-group-type="heading">
          <subject>Original Article</subject>
        </subj-group>
        <subj-group subj-group-type="scientific_subject">
          <subject>Diagnostic medicine</subject>
          <subject>Infectious diseases</subject>
          <subject>Microbiology</subject>
          <subject>Molecular biology</subject>
        </subj-group>
      </article-categories>
      <title-group>
        <article-title>Azithromycin treatment failure and macrolide resistance in <italic><tp:taxon-name><tp:taxon-name-part taxon-name-part-type="genus" reg="Mycoplasma">Mycoplasma</tp:taxon-name-part> <tp:taxon-name-part taxon-name-part-type="species" reg="genitalium">genitalium</tp:taxon-name-part></tp:taxon-name></italic> infections in Sofia, Bulgaria</article-title>
      </title-group>
      <contrib-group content-type="authors">
        <contrib contrib-type="author" corresp="yes">
          <name name-style="western">
            <surname>Philipova</surname>
            <given-names>Ivva</given-names>
          </name>
          <email xlink:type="simple">ivva.philipova@ncipd.org</email>
          <uri content-type="orcid">https://orcid.org/0000-0003-4299-4827</uri>
          <xref ref-type="aff" rid="A1">1</xref>
        </contrib>
        <contrib contrib-type="author" corresp="no">
          <name name-style="western">
            <surname>Levterova</surname>
            <given-names>Viktoryia</given-names>
          </name>
          <xref ref-type="aff" rid="A1">1</xref>
        </contrib>
        <contrib contrib-type="author" corresp="no">
          <name name-style="western">
            <surname>Simeonovski</surname>
            <given-names>Ivan</given-names>
          </name>
          <xref ref-type="aff" rid="A1">1</xref>
        </contrib>
        <contrib contrib-type="author" corresp="no">
          <name name-style="western">
            <surname>Kantardjiev</surname>
            <given-names>Todor</given-names>
          </name>
          <xref ref-type="aff" rid="A1">1</xref>
        </contrib>
      </contrib-group>
      <aff id="A1">
        <label>1</label>
        <addr-line content-type="verbatim">National Center of Infectious and Parasitic Diseases, Department of Microbiology, Sofia, Bulgaria</addr-line>
        <institution>National Center of Infectious and Parasitic Diseases</institution>
        <addr-line content-type="city">Sofia</addr-line>
        <country>Bulgaria</country>
      </aff>
      <author-notes>
        <fn fn-type="corresp">
          <p>Corresponding author: Ivva Philipova, National Center of Infectious and Parasitic Diseases, Department of Microbiology, 26 Yanko Sakazov Blvd., 1504 Sofia, Bulgaria; Email: <email xlink:type="simple">ivva.philipova@ncipd.org</email>; Tel.: +359 884 347 612</p>
        </fn>
      </author-notes>
      <pub-date pub-type="collection">
        <year>2022</year>
      </pub-date>
      <pub-date pub-type="epub">
        <day>30</day>
        <month>06</month>
        <year>2022</year>
      </pub-date>
      <volume>64</volume>
      <issue>3</issue>
      <fpage>422</fpage>
      <lpage>429</lpage>
      <uri content-type="arpha" xlink:href="http://openbiodiv.net/6EDF8912-455A-5F78-9227-A85746283007">6EDF8912-455A-5F78-9227-A85746283007</uri>
      <history>
        <date date-type="received">
          <day>26</day>
          <month>01</month>
          <year>2021</year>
        </date>
        <date date-type="accepted">
          <day>18</day>
          <month>05</month>
          <year>2021</year>
        </date>
      </history>
      <permissions>
        <copyright-statement>Ivva Philipova, Viktoryia Levterova, Ivan Simeonovski, Todor Kantardjiev</copyright-statement>
        <license license-type="creative-commons-attribution" xlink:href="http://creativecommons.org/licenses/by/4.0/" xlink:type="simple">
          <license-p>This is an open access article distributed under the terms of the Creative Commons Attribution License (CC BY 4.0), which permits unrestricted use, distribution, and reproduction in any medium, provided the original author and source are credited.</license-p>
        </license>
      </permissions>
      <abstract>
        <label>Abstract</label>
        <p><bold>Introduction</bold>: <italic><tp:taxon-name><tp:taxon-name-part taxon-name-part-type="genus" reg="Mycoplasma">Mycoplasma</tp:taxon-name-part> <tp:taxon-name-part taxon-name-part-type="species" reg="genitalium">genitalium</tp:taxon-name-part></tp:taxon-name></italic> is an established cause of sexually transmitted infections in men and women. Current guidelines recommend azithromycin and moxifloxacin as first- and second-line treatment, respectively. However, azithromycin treatment failure has been increasingly reported. The aim of this study was to determine the efficacy of azithromycin and alternative antibiotic regimens in a prospective cohort of <italic><tp:taxon-name><tp:taxon-name-part taxon-name-part-type="genus" reg="Mycoplasma">M.</tp:taxon-name-part> <tp:taxon-name-part taxon-name-part-type="species" reg="genitalium">genitalium</tp:taxon-name-part></tp:taxon-name></italic>-positive patients, and macrolide resistance mutations associated with azithromycin failure.</p>
        <p><bold>Materials and methods</bold>: Consecutive eligible <italic><tp:taxon-name><tp:taxon-name-part taxon-name-part-type="genus" reg="Mycoplasma">M.</tp:taxon-name-part> <tp:taxon-name-part taxon-name-part-type="species" reg="genitalium">genitalium</tp:taxon-name-part></tp:taxon-name></italic>-positive patients attending the National Center of Infectious and Parasitic Diseases in Sofia, Bulgaria between 1 January 2018 and 31 December 2020 were treated with azithromycin and retested by polymerase chain reaction 21-28 days after completion of the treatment. Cure was defined as <italic><tp:taxon-name><tp:taxon-name-part taxon-name-part-type="genus" reg="Mycoplasma">M.</tp:taxon-name-part> <tp:taxon-name-part taxon-name-part-type="species" reg="genitalium">genitalium</tp:taxon-name-part></tp:taxon-name></italic>-negative result on the test of cure. Cases failing azithromycin were treated with moxifloxacin and retested another 21-28 days after treatment. Pre- and post-treatment samples were assessed for macrolide resistance mutations by conventional DNA sequencing.</p>
        <p><bold>Results</bold>: Of 21 patients treated with azithromycin, 11 (52.4%) were cured. Pre- and post-treatment macrolide resistance mutations were detected in 10 (47.6%) patients, and all of them failed azithromycin. Moxifloxacin was effective in all cases failing azithromycin; and all were <italic><tp:taxon-name><tp:taxon-name-part taxon-name-part-type="genus" reg="Mycoplasma">M.</tp:taxon-name-part> <tp:taxon-name-part taxon-name-part-type="species" reg="genitalium">genitalium</tp:taxon-name-part></tp:taxon-name></italic>-negative at the test of cure after moxifloxacin treatment.</p>
        <p><bold>Conclusions</bold>: In this study a high azithromycin failure rate (47.6%) in an <italic><tp:taxon-name><tp:taxon-name-part taxon-name-part-type="genus" reg="Mycoplasma">M.</tp:taxon-name-part> <tp:taxon-name-part taxon-name-part-type="species" reg="genitalium">genitalium</tp:taxon-name-part></tp:taxon-name></italic>-positive cohort in association with high levels of pretreatment macrolide resistance was reported. Moxifloxacin was highly effective in treating macrolide-resistant infections. These findings necessitate implementation of new diagnostic and therapeutic strategies such as sequential antimicrobial therapy for <italic><tp:taxon-name><tp:taxon-name-part taxon-name-part-type="genus" reg="Mycoplasma">M.</tp:taxon-name-part> <tp:taxon-name-part taxon-name-part-type="species" reg="genitalium">genitalium</tp:taxon-name-part></tp:taxon-name></italic> guided by a macrolide-resistance assay.</p>
      </abstract>
      <kwd-group>
        <label>Keywords</label>
        <kwd>antimicrobial resistance</kwd>
        <kwd>azithromycin failure</kwd>
        <kwd>Bulgaria</kwd>
        <kwd>
          <italic>
            <tp:taxon-name><tp:taxon-name-part taxon-name-part-type="genus" reg="Mycoplasma">Mycoplasma</tp:taxon-name-part> <tp:taxon-name-part taxon-name-part-type="species" reg="genitalium">genitalium</tp:taxon-name-part></tp:taxon-name>
          </italic>
        </kwd>
      </kwd-group>
      <funding-group>
        <award-group>
          <funding-source>
            <named-content content-type="funder_name">Bulgarian National Science Fund</named-content>
            <named-content content-type="funder_identifier">501100003336</named-content>
            <named-content content-type="funder_doi">http://doi.org/10.13039/501100003336</named-content>
          </funding-source>
        </award-group>
      </funding-group>
    </article-meta>
  </front>
  <body>
    <sec sec-type="Introduction" id="SECID0ESH">
      <title>Introduction</title>
      <p><italic><tp:taxon-name>
            <tp:taxon-name-part taxon-name-part-type="genus" reg="Mycoplasma">Mycoplasma</tp:taxon-name-part> <tp:taxon-name-part taxon-name-part-type="species" reg="genitalium">genitalium</tp:taxon-name-part></tp:taxon-name></italic> was first isolated in 1980 in samples from patients with urogenital infections.<sup>[<xref ref-type="bibr" rid="B1">1</xref>]</sup> Because of the fastidious growth of the bacterium in culture, its etiological role as pathogen was in discussion for many years. Meanwhile, <italic><tp:taxon-name><tp:taxon-name-part taxon-name-part-type="genus" reg="Mycoplasma">M.</tp:taxon-name-part> <tp:taxon-name-part taxon-name-part-type="species" reg="genitalium">genitalium</tp:taxon-name-part></tp:taxon-name></italic> is an established agent of sexually transmitted infections such as nongonoccocal urethritis (NGU) and cervicitis, and it is implicated in pelvic inflammatory disease<sup>[<xref ref-type="bibr" rid="B2">2</xref>,3]</sup> and increases transmission of human immunodeficiency virus<sup>[<xref ref-type="bibr" rid="B4">4</xref>]</sup>. Like other mycoplasma species, <italic><tp:taxon-name><tp:taxon-name-part taxon-name-part-type="genus" reg="Mycoplasma">M.</tp:taxon-name-part> <tp:taxon-name-part taxon-name-part-type="species" reg="genitalium">genitalium</tp:taxon-name-part></tp:taxon-name></italic> possesses a highly reduced genome and lacks a peptidoglycan-containing cell wall, so fewer classes of available antimicrobial agents are effective including tetracyclines, macrolides and fluoroquinolones.</p>
      <p>Although <italic>in vitro</italic> studies suggest that <italic><tp:taxon-name><tp:taxon-name-part taxon-name-part-type="genus" reg="Mycoplasma">M.</tp:taxon-name-part> <tp:taxon-name-part taxon-name-part-type="species" reg="genitalium">genitalium</tp:taxon-name-part></tp:taxon-name></italic> is highly susceptible against doxycycline, this drug has a poor clinical efficacy with microbiological cure rates between 22% and 45%.<sup>[<xref ref-type="bibr" rid="B5">5</xref>]</sup> Doxycycline is therefore not recommended for first-line treatment by European, US, and UK guidelines.<sup>[<xref ref-type="bibr" rid="B6 B7 B8">6–8</xref>]</sup></p>
      <p>Azithromycin given as an extended regimen is recommended as the primary choice for treatment of <italic><tp:taxon-name><tp:taxon-name-part taxon-name-part-type="genus" reg="Mycoplasma">M.</tp:taxon-name-part> <tp:taxon-name-part taxon-name-part-type="species" reg="genitalium">genitalium</tp:taxon-name-part></tp:taxon-name></italic> infections with a cure rate of approximately 85%.<sup>[<xref ref-type="bibr" rid="B6 B7 B8 B9">6–9</xref>]</sup> However, the emergence of macrolide resistance is drastically decreasing the overall cure rate over the past decade with pooled cure rates in studies prior to 2009 of 85% compared to 67% in studies since 2009.<sup>[<xref ref-type="bibr" rid="B10">10</xref>]</sup> Macrolide resistance rates vary significantly geographically, but where azithromycin has been widely utilized, it is usually found in 30%–45% of samples.<sup>[<xref ref-type="bibr" rid="B11 B12 B13 B14 B15">11–15</xref>]</sup></p>
      <p>Moxifloxacin is the most commonly recommended agent as second-line antimicrobial treatment.<sup>[<xref ref-type="bibr" rid="B6 B7 B8">6–8</xref>]</sup> It is bactericidal and has a cure rate approaching 100% in infections with susceptible strains.<sup>[<xref ref-type="bibr" rid="B16">16</xref>]</sup> Unfortunately, resistance has developed with treatment failures in up to 12%, primarily in the Asia-Pacific region.<sup>[<xref ref-type="bibr" rid="B17">17</xref>]</sup></p>
    </sec>
    <sec sec-type="Aim" id="SECID0EFEAC">
      <title>Aim</title>
      <p>This observational study has the aim to determine the <italic><tp:taxon-name><tp:taxon-name-part taxon-name-part-type="genus" reg="Mycoplasma">M.</tp:taxon-name-part> <tp:taxon-name-part taxon-name-part-type="species" reg="genitalium">genitalium</tp:taxon-name-part></tp:taxon-name></italic> microbial cure rate of azithromycin and to evaluate the contribution of macrolide resistance mutations to azithromycin failure. Effectiveness of moxifloxacin is determined in cases failing azithromycin.</p>
    </sec>
    <sec sec-type="materials|methods" id="SECID0EWEAC">
      <title>Materials and methods</title>
      <sec sec-type="Recruitment and patient management" id="SECID0E1EAC">
        <title>Recruitment and patient management</title>
        <p>This observational study was conducted between 1 January 2018 and 31 December 2020 at the National Center of Infectious and Parasitic Diseases in Sofia, Bulgaria. Routine testing for <italic><tp:taxon-name><tp:taxon-name-part taxon-name-part-type="genus" reg="Mycoplasma">M.</tp:taxon-name-part> <tp:taxon-name-part taxon-name-part-type="species" reg="genitalium">genitalium</tp:taxon-name-part></tp:taxon-name></italic> was performed in patients with nongonoccocal urethritis (NGU), cervicitis and/or pelvic inflammatory disease, and sexual contacts of infected partners. Eligible participants were patients aged 18 years and older, diagnosed with <italic><tp:taxon-name><tp:taxon-name-part taxon-name-part-type="genus" reg="Mycoplasma">M.</tp:taxon-name-part> <tp:taxon-name-part taxon-name-part-type="species" reg="genitalium">genitalium</tp:taxon-name-part></tp:taxon-name></italic> and treated with azithromycin as first-line therapy. Participants were asked to abstain from sexual activity for the duration of study and to return for a test of cure (TOC) 21 days after completing treatment with azithromycin. Cases returning a TOC within 56 days of treatment completion were included in analyses to allow for delay in re-attendance for TOC. Along with the TOC, key data were collected to evaluate patient compliance and reinfection risk, including persistence of symptoms, adherence to antibiotic dosing regimen, adverse events and post-treatment sexual exposure to new or continuing partners. Where reinfection was suspected, index patients and contactable partners were recalled and retreated simultaneously with azithromycin. Only data following retreatment were included in analyses. Patients who remained <italic><tp:taxon-name><tp:taxon-name-part taxon-name-part-type="genus" reg="Mycoplasma">M.</tp:taxon-name-part> <tp:taxon-name-part taxon-name-part-type="species" reg="genitalium">genitalium</tp:taxon-name-part></tp:taxon-name></italic>-positive at the TOC following azithromycin, and who had no reinfection risk, were given moxifloxacin, and retested 21 days after completing treatment. All eligible participants were treated with antimicrobial therapeutic regimens recommended by the IUSTI 2016 European guideline on <italic><tp:taxon-name><tp:taxon-name-part taxon-name-part-type="genus" reg="Mycoplasma">Mycoplasma</tp:taxon-name-part> <tp:taxon-name-part taxon-name-part-type="species" reg="genitalium">genitalium</tp:taxon-name-part></tp:taxon-name></italic> infections.<sup>[<xref ref-type="bibr" rid="B7">7</xref>]</sup></p>
        <p>Azithromycin efficacy was measured as <italic><tp:taxon-name><tp:taxon-name-part taxon-name-part-type="genus" reg="Mycoplasma">M.</tp:taxon-name-part> <tp:taxon-name-part taxon-name-part-type="species" reg="genitalium">genitalium</tp:taxon-name-part></tp:taxon-name></italic> microbial cure following treatment with azithromycin. Microbial cure was calculated as follows: numerator = number of participants treated by azithromycin who were microbiologically cured of <italic><tp:taxon-name><tp:taxon-name-part taxon-name-part-type="genus" reg="Mycoplasma">M.</tp:taxon-name-part> <tp:taxon-name-part taxon-name-part-type="species" reg="genitalium">genitalium</tp:taxon-name-part></tp:taxon-name></italic> (defined as a TOC <italic><tp:taxon-name><tp:taxon-name-part taxon-name-part-type="genus" reg="Mycoplasma">M.</tp:taxon-name-part> <tp:taxon-name-part taxon-name-part-type="species" reg="genitalium">genitalium</tp:taxon-name-part></tp:taxon-name></italic>-negative at follow-up); denominator = all those treated with azithromycin for <italic><tp:taxon-name><tp:taxon-name-part taxon-name-part-type="genus" reg="Mycoplasma">M.</tp:taxon-name-part> <tp:taxon-name-part taxon-name-part-type="species" reg="genitalium">genitalium</tp:taxon-name-part></tp:taxon-name></italic> and tested at follow-up. For both the denominator and numerator, only those who were followed up were included.</p>
        <p>Azithromycin failure was defined as <italic><tp:taxon-name><tp:taxon-name-part taxon-name-part-type="genus" reg="Mycoplasma">M.</tp:taxon-name-part> <tp:taxon-name-part taxon-name-part-type="species" reg="genitalium">genitalium</tp:taxon-name-part></tp:taxon-name></italic>-positive at TOC (with or without persistent symptoms) with no reinfection risk.</p>
      </sec>
      <sec sec-type="methods" id="SECID0ENIAC">
        <title>Laboratory methods</title>
        <p>All examined specimens were sampled and stored as part of the routine STIs diagnostics (standard care) at National Center of Infectious and Parasitic Diseases as follows: forty millilitres of first-void urine specimen were centrifuged for 15 minutes at 2500 g and the pellet was resuspended in 200 µL of Tris-EDTA buffer solution (TE Buffer). Genital swabs were rotated 10 times in 400 µL of TE Buffer. Two hundred microliters of TE Buffer containing urine pellet or swab cells were then extracted using AmpliSens<sup>®</sup> MAGNO-sorb-URO nucleic acid extraction kit (Ecoli s.r.o., Slovak Republic) as per manufacturer instructions. Detection of <italic><tp:taxon-name><tp:taxon-name-part taxon-name-part-type="genus" reg="Mycoplasma">M.</tp:taxon-name-part> <tp:taxon-name-part taxon-name-part-type="species" reg="genitalium">genitalium</tp:taxon-name-part></tp:taxon-name></italic> DNA was performed by AmpliSens<sup>®</sup><tp:taxon-name><tp:taxon-name-part taxon-name-part-type="genus" reg="Mycoplasma">Mycoplasma</tp:taxon-name-part> <tp:taxon-name-part taxon-name-part-type="species" reg="genitalium">genitalium</tp:taxon-name-part></tp:taxon-name>-FRT.<sup>[<xref ref-type="bibr" rid="B18">18</xref>,19]</sup> All <italic><tp:taxon-name><tp:taxon-name-part taxon-name-part-type="genus" reg="Mycoplasma">M.</tp:taxon-name-part> <tp:taxon-name-part taxon-name-part-type="species" reg="genitalium">genitalium</tp:taxon-name-part></tp:taxon-name></italic> molecular diagnostics were performed on fresh samples during the study period 2018-2020. Immediately after <italic><tp:taxon-name><tp:taxon-name-part taxon-name-part-type="genus" reg="Mycoplasma">M.</tp:taxon-name-part> <tp:taxon-name-part taxon-name-part-type="species" reg="genitalium">genitalium</tp:taxon-name-part></tp:taxon-name></italic> diagnostics, the samples were stored at −79°C.</p>
        <p>In January 2019, January 2020, and December 2020 currently available <italic><tp:taxon-name><tp:taxon-name-part taxon-name-part-type="genus" reg="Mycoplasma">M.</tp:taxon-name-part> <tp:taxon-name-part taxon-name-part-type="species" reg="genitalium">genitalium</tp:taxon-name-part></tp:taxon-name></italic>-positive samples were subjected to further molecular analysis. Firstly, positive samples were confirmed by PCR detecting the <italic>MgPa</italic> adhesion gene<sup>[<xref ref-type="bibr" rid="B20">20</xref>]</sup>, then resistance-associated mutations in the 23S ribosomal RNA (rRNA) gene were identified using conventional Sanger DNA sequencing of the 147 bp amplicon produced with primers Mg23S-1992F and Mg23S-2138R, as described previously.<sup>[<xref ref-type="bibr" rid="B21">21</xref>]</sup> Sequence editing and multiple sequence alignments were performed using the software CLC Main Workbench, version 20.0.4 (<ext-link xlink:type="simple" ext-link-type="uri" xlink:href="https://digitalinsights.qiagen.com">https://digitalinsights.qiagen.com</ext-link>).</p>
      </sec>
      <sec sec-type="Ethics and informed consent" id="SECID0ELLAC">
        <title>Ethics and informed consent</title>
        <p>Written informed consents were obtained from eligible patients for personal data collection and microbiological sample testing as required by national law and the Ethics Committee at the National Center for Infectious and Parasitic Diseases, Sofia, Bulgaria.</p>
      </sec>
    </sec>
    <sec sec-type="Results" id="SECID0EQLAC">
      <title>Results</title>
      <p>Twenty-five patients were diagnosed with <italic><tp:taxon-name><tp:taxon-name-part taxon-name-part-type="genus" reg="Mycoplasma">M.</tp:taxon-name-part> <tp:taxon-name-part taxon-name-part-type="species" reg="genitalium">genitalium</tp:taxon-name-part></tp:taxon-name></italic> during the study period <bold>(Fig. <xref ref-type="fig" rid="F1">1</xref>)</bold>. Three patients were ineligible as they did not receive azithromycin as first-line therapy. Of the 22 enrolled participants, 21 (95.5%) completed all aspects of the study. One participant did not provide follow-up samples within 56 days, although lab technicians made at least two attempts to contact those who failed to attend. None of the eligible participants was previously tested positive for <italic><tp:taxon-name><tp:taxon-name-part taxon-name-part-type="genus" reg="Mycoplasma">M.</tp:taxon-name-part> <tp:taxon-name-part taxon-name-part-type="species" reg="genitalium">genitalium</tp:taxon-name-part></tp:taxon-name></italic>.</p>
      <p>Of the enrolled participants, 18 (85.7%) patients were men and 3 (14.3%) were women <bold>(Table <xref ref-type="table" rid="T1">1</xref>)</bold>. Fifteen (83.3%) <italic><tp:taxon-name><tp:taxon-name-part taxon-name-part-type="genus" reg="Mycoplasma">M.</tp:taxon-name-part> <tp:taxon-name-part taxon-name-part-type="species" reg="genitalium">genitalium</tp:taxon-name-part></tp:taxon-name></italic>-positive males had symptomatic NGU and 3 (5%) were asymptomatic contacts, whereas the 2 of <italic><tp:taxon-name><tp:taxon-name-part taxon-name-part-type="genus" reg="Mycoplasma">M.</tp:taxon-name-part> <tp:taxon-name-part taxon-name-part-type="species" reg="genitalium">genitalium</tp:taxon-name-part></tp:taxon-name></italic>-positive females presented as asymptomatic contacts of males and the remaining 1 symptomatic female reported vaginal symptoms.</p>
      <table-wrap id="T1" position="float" orientation="portrait">
        <label>Table 1.</label>
        <caption>
          <p>Characteristics of participants</p>
        </caption>
        <table id="TID0EFKAE" rules="all">
          <tbody>
            <tr>
              <td rowspan="1" colspan="1"/>
              <td rowspan="1" colspan="1">
                <bold>Male (n=18) n (%)</bold>
              </td>
              <td rowspan="1" colspan="1">
                <bold>Female (n=3) n (%)</bold>
              </td>
            </tr>
            <tr>
              <td rowspan="1" colspan="1">Median age (range)</td>
              <td rowspan="1" colspan="1">32 (22-49)</td>
              <td rowspan="1" colspan="1">28 (23-33)</td>
            </tr>
            <tr>
              <td rowspan="1" colspan="1">Presentation</td>
              <td rowspan="1" colspan="1"/>
              <td rowspan="1" colspan="1"/>
            </tr>
            <tr>
              <td rowspan="1" colspan="1">Symptomatic</td>
              <td rowspan="1" colspan="1">15 (83.3)</td>
              <td rowspan="1" colspan="1">1 (33.3)</td>
            </tr>
            <tr>
              <td rowspan="1" colspan="1">Asymptomatic contact</td>
              <td rowspan="1" colspan="1">3 (16.7)</td>
              <td rowspan="1" colspan="1">2 (66.7)</td>
            </tr>
            <tr>
              <td rowspan="1" colspan="1">Specimen</td>
              <td rowspan="1" colspan="1"/>
              <td rowspan="1" colspan="1"/>
            </tr>
            <tr>
              <td rowspan="1" colspan="1">First-void urine</td>
              <td rowspan="1" colspan="1">14 (77.8)</td>
              <td rowspan="1" colspan="1">0 (0)</td>
            </tr>
            <tr>
              <td rowspan="1" colspan="1">Genital swab</td>
              <td rowspan="1" colspan="1">4 (22.2)</td>
              <td rowspan="1" colspan="1">3 (100)</td>
            </tr>
          </tbody>
        </table>
      </table-wrap>
      <fig id="F1" position="float" orientation="portrait">
        <object-id content-type="arpha">9A7A55DC-8FA4-536A-8B16-983A4FA7D271</object-id>
        <label>Figure 1.</label>
        <caption>
          <p>Recruitment and participation. TOC: test of cure.</p>
        </caption>
        <graphic xlink:href="foliamedica-64-3-e63624-g001.jpg" position="float" orientation="portrait" xlink:type="simple" id="oo_708464.jpg">
          <uri content-type="original_file">https://binary.pensoft.net/fig/708464</uri>
        </graphic>
      </fig>
      <sec sec-type="Azithromycin treatment outcomes" id="SECID0ESNAC">
        <title>Azithromycin treatment outcomes</title>
        <p>Eleven cases had a <italic><tp:taxon-name><tp:taxon-name-part taxon-name-part-type="genus" reg="Mycoplasma">M.</tp:taxon-name-part> <tp:taxon-name-part taxon-name-part-type="species" reg="genitalium">genitalium</tp:taxon-name-part></tp:taxon-name></italic>-negative TOC, yielding an azithromycin cure rate of 52.4% (95% CI, 29.8% - 74.3%). Ten patients failed azithromycin (47.6% [95% CI, 25.7%-70.2%]) as they were <italic><tp:taxon-name><tp:taxon-name-part taxon-name-part-type="genus" reg="Mycoplasma">M.</tp:taxon-name-part> <tp:taxon-name-part taxon-name-part-type="species" reg="genitalium">genitalium</tp:taxon-name-part></tp:taxon-name></italic>-positive at TOC with no reinfection risk and received moxifloxacin as second-line therapy. Following treatment, one participant reported post-treatment sexual activity with an untreated partner. The index patient and the untreated partner were successfully recalled, retreated simultaneously with azithromycin, and recommenced participation, with only data following retreatment included in analyses.</p>
      </sec>
      <sec sec-type="Macrolide resistance mutations in pre- and post-treatment M. genitalium-positive samples" id="SECID0EOOAC">
        <title>Macrolide resistance mutations in pre- and post-treatment <italic><tp:taxon-name><tp:taxon-name-part taxon-name-part-type="genus" reg="Mycoplasma">M.</tp:taxon-name-part> <tp:taxon-name-part taxon-name-part-type="species" reg="genitalium">genitalium</tp:taxon-name-part></tp:taxon-name></italic>-positive samples</title>
        <p>Overall, 23S rRNA gene sequences spanning positions 2071 and 2072 (2058 and 2059, <italic><tp:taxon-name><tp:taxon-name-part taxon-name-part-type="genus" reg="Escherichia">Escherichia</tp:taxon-name-part> <tp:taxon-name-part taxon-name-part-type="species" reg="coli">coli</tp:taxon-name-part></tp:taxon-name></italic> numbering) were obtained for the 21 pre-treatment <italic><tp:taxon-name><tp:taxon-name-part taxon-name-part-type="genus" reg="Mycoplasma">M.</tp:taxon-name-part> <tp:taxon-name-part taxon-name-part-type="species" reg="genitalium">genitalium</tp:taxon-name-part></tp:taxon-name></italic> samples in this study <bold>(Fig. <xref ref-type="fig" rid="F2">2</xref>)</bold>.</p>
        <p>Additionally, 10 post-treatment samples from individuals with azithromycin treatment failure were tested for macrolide resistance mutations. On the pre-treatment samples, 11 (52.4%) cases had a wild type 23S rRNA gene sequence and had <italic><tp:taxon-name><tp:taxon-name-part taxon-name-part-type="genus" reg="Mycoplasma">M.</tp:taxon-name-part> <tp:taxon-name-part taxon-name-part-type="species" reg="genitalium">genitalium</tp:taxon-name-part></tp:taxon-name></italic>-negative TOC and azithromycin cure, respectively. All of the 10 participants with azithromycin treatment failure were shown to possess 23S rRNA gene mutations in pre- and post-treatment samples, consisting of A2072G (A2059G), A2071G (A2058G), and A2071T (A2058T). Amino acids substitutions in <italic><tp:taxon-name><tp:taxon-name-part taxon-name-part-type="genus" reg="Escherichia">E.</tp:taxon-name-part> <tp:taxon-name-part taxon-name-part-type="species" reg="coli">coli</tp:taxon-name-part></tp:taxon-name></italic>, to which those in <italic><tp:taxon-name><tp:taxon-name-part taxon-name-part-type="genus" reg="Mycoplasma">M.</tp:taxon-name-part> <tp:taxon-name-part taxon-name-part-type="species" reg="genitalium">genitalium</tp:taxon-name-part></tp:taxon-name></italic> respectively correspond, are given in the parentheses. In all of the resistant cases, mutational changes of the same type were detected in both the pre- and post-treatment samples indicating transmitted resistance <bold>(Table <xref ref-type="table" rid="T2">2</xref>)</bold>. The most common mutation was A2072G (70%), followed by A2071G (20%) and A2071T (10%). No selected resistant <italic><tp:taxon-name><tp:taxon-name-part taxon-name-part-type="genus" reg="Mycoplasma">M.</tp:taxon-name-part> <tp:taxon-name-part taxon-name-part-type="species" reg="genitalium">genitalium</tp:taxon-name-part></tp:taxon-name></italic> strains were identified (wild type 23S rRNA gene sequence on the pre-treatment sample and macrolide resistant mutation detected on post-treatment samples).</p>
        <table-wrap id="T2" position="float" orientation="portrait">
          <label>Table 2.</label>
          <caption>
            <p>23S rRNA gene sequence in pre- and post-treatment samples</p>
          </caption>
          <table id="TID0ELPAE" rules="all">
            <tbody>
              <tr>
                <td rowspan="1" colspan="1">
                  <bold>23S rRNA</bold>
                </td>
                <td rowspan="1" colspan="1">
                  <bold>Pretreatment samples (n=21), No. (%)</bold>
                </td>
                <td rowspan="1" colspan="1">
                  <bold>Posttreatment sample (n=10), No. (%)</bold>
                </td>
              </tr>
              <tr>
                <td rowspan="1" colspan="1">WT</td>
                <td rowspan="1" colspan="1">11 (52.4)</td>
                <td rowspan="1" colspan="1">0(0)</td>
              </tr>
              <tr>
                <td rowspan="1" colspan="1">A2071G (A2058G*)</td>
                <td rowspan="1" colspan="1">2 (9.5)</td>
                <td rowspan="1" colspan="1">2 (20)</td>
              </tr>
              <tr>
                <td rowspan="1" colspan="1">A2071T (A2058T*)</td>
                <td rowspan="1" colspan="1">1 (4.8)</td>
                <td rowspan="1" colspan="1">1 (10)</td>
              </tr>
              <tr>
                <td rowspan="1" colspan="1">A2072G (A2059G*)</td>
                <td rowspan="1" colspan="1">7 (33.3)</td>
                <td rowspan="1" colspan="1">7 (70)</td>
              </tr>
              <tr>
                <td rowspan="1" colspan="1">*<italic><tp:taxon-name><tp:taxon-name-part taxon-name-part-type="genus" reg="Escherichia">E.</tp:taxon-name-part> <tp:taxon-name-part taxon-name-part-type="species" reg="coli">coli</tp:taxon-name-part></tp:taxon-name></italic> numbering</td>
                <td rowspan="1" colspan="1"/>
                <td rowspan="1" colspan="1"/>
              </tr>
            </tbody>
          </table>
        </table-wrap>
        <fig id="F2" position="float" orientation="portrait">
          <object-id content-type="arpha">195AEB2A-F00E-54AF-B7C6-A59D05B5CFE2</object-id>
          <label>Figure 2.</label>
          <caption>
            <p>Comparison of partial sequences of 23S rRNA gene for <italic><tp:taxon-name><tp:taxon-name-part taxon-name-part-type="genus" reg="Mycoplasma">M.</tp:taxon-name-part> <tp:taxon-name-part taxon-name-part-type="species" reg="genitalium">genitalium</tp:taxon-name-part></tp:taxon-name></italic>-positive specimens detected in this study to the wild-type sequence (NCBI Reference Sequence: NR_077054.1) and macrolide resistant strains previously characterized at Statens Serum Institute (Copenhagen, Denmark) (Accession numbers M6321, M50367 and W68551).<sup>[22]</sup></p>
          </caption>
          <graphic xlink:href="foliamedica-64-3-e63624-g002.jpg" position="float" orientation="portrait" xlink:type="simple" id="oo_708465.jpg">
            <uri content-type="original_file">https://binary.pensoft.net/fig/708465</uri>
          </graphic>
        </fig>
      </sec>
      <sec sec-type="Effectiveness of alternative agents for M. genitalium-infections failing azithromycin" id="SECID0ETBAE">
        <title>Effectiveness of alternative agents for <italic><tp:taxon-name><tp:taxon-name-part taxon-name-part-type="genus" reg="Mycoplasma">M.</tp:taxon-name-part> <tp:taxon-name-part taxon-name-part-type="species" reg="genitalium">genitalium</tp:taxon-name-part></tp:taxon-name></italic>-infections failing azithromycin</title>
        <p>All 10 participants who failed azithromycin were given moxifloxacin and were <italic><tp:taxon-name><tp:taxon-name-part taxon-name-part-type="genus" reg="Mycoplasma">M.</tp:taxon-name-part> <tp:taxon-name-part taxon-name-part-type="species" reg="genitalium">genitalium</tp:taxon-name-part></tp:taxon-name></italic>-negative at TOC after the second-line therapy, yielding a moxifloxacin cure rate of 100%.</p>
      </sec>
    </sec>
    <sec sec-type="Discussion" id="SECID0EQCAE">
      <title>Discussion</title>
      <p>In this study, we report a high failure rate (47.6%) of azithromycin first-line therapy and high levels of macrolide resistance in <italic><tp:taxon-name><tp:taxon-name-part taxon-name-part-type="genus" reg="Mycoplasma">M.</tp:taxon-name-part> <tp:taxon-name-part taxon-name-part-type="species" reg="genitalium">genitalium</tp:taxon-name-part></tp:taxon-name></italic>-positive patients from Sofia, Bulgaria. Azithromycin failure was attributable to transmitted resistance and no selected resistance was detected after receiving azithromycin. Moxifloxacin was effective in all cases failing azithromycin.</p>
      <p>Azithromycin remains the recommended first-line treatment for <italic><tp:taxon-name><tp:taxon-name-part taxon-name-part-type="genus" reg="Mycoplasma">M.</tp:taxon-name-part> <tp:taxon-name-part taxon-name-part-type="species" reg="genitalium">genitalium</tp:taxon-name-part></tp:taxon-name></italic> infection<sup>[<xref ref-type="bibr" rid="B6 B7 B8">6–8</xref>]</sup>, although international data reveal that azithromycin is becoming less effective and macrolide resistance is increasing<sup>[<xref ref-type="bibr" rid="B23 B24 B25 B26 B27 B28">23–28</xref>]</sup>. Data from Bulgarian studies remain very scarce, reporting <italic><tp:taxon-name><tp:taxon-name-part taxon-name-part-type="genus" reg="Mycoplasma">M.</tp:taxon-name-part> <tp:taxon-name-part taxon-name-part-type="species" reg="genitalium">genitalium</tp:taxon-name-part></tp:taxon-name></italic> solely prevalence with rates ranging from 0.29% to 2.45%.<sup>[<xref ref-type="bibr" rid="B29 B30 B31">29–31</xref>]</sup> To the knowledge of the authors, this is the first observational study for azithromycin failure and macrolide resistance in <italic><tp:taxon-name><tp:taxon-name-part taxon-name-part-type="genus" reg="Mycoplasma">M.</tp:taxon-name-part> <tp:taxon-name-part taxon-name-part-type="species" reg="genitalium">genitalium</tp:taxon-name-part></tp:taxon-name></italic>-positive patients from Bulgaria. The obtained in this study azithromycin cure rate of 52.4% is alarmingly low and raises concerns over the continued use of azithromycin in Bulgarian population, making the investigation of new diagnostic and therapeutic strategies a priority.</p>
      <p>Failure of azithromycin is strongly associated with macrolide resistance mutations in the 23S rRNA molecule within the 50S subunit of the bacterial ribosome. These single-nucleotide polymorphisms in position 2071 and 2072 (2058 and 2059, <italic><tp:taxon-name><tp:taxon-name-part taxon-name-part-type="genus" reg="Escherichia">E.</tp:taxon-name-part> <tp:taxon-name-part taxon-name-part-type="species" reg="coli">coli</tp:taxon-name-part></tp:taxon-name></italic> numbering) in region V of the 23S rRNA gene confer high-level resistance to azithromycin.‌<sup>[22,32-34]</sup> According to recent scientific publications, differences in sexually transmitted infections management and treatment may distinctly influence antimicrobial resistance in <italic><tp:taxon-name><tp:taxon-name-part taxon-name-part-type="genus" reg="Mycoplasma">M.</tp:taxon-name-part> <tp:taxon-name-part taxon-name-part-type="species" reg="genitalium">genitalium</tp:taxon-name-part></tp:taxon-name></italic> among European regions.<sup>[<xref ref-type="bibr" rid="B35">35</xref>]</sup> For example, in countries like Sweden<sup>[<xref ref-type="bibr" rid="B36">36</xref>]</sup> where doxycycline is the preferred first-line treatment for NGU and <italic><tp:taxon-name><tp:taxon-name-part taxon-name-part-type="genus" reg="Chlamydia">C.</tp:taxon-name-part> <tp:taxon-name-part taxon-name-part-type="species" reg="trachomatis">trachomatis</tp:taxon-name-part></tp:taxon-name></italic>, the reported macrolide resistance is among the lowest in Europe (12.1%). On the contrary, high rates of macrolide resistance have been reported by countries using azithromycin as empirical treatment for NGU and <italic><tp:taxon-name><tp:taxon-name-part taxon-name-part-type="genus" reg="Chlamydia">C.</tp:taxon-name-part> <tp:taxon-name-part taxon-name-part-type="species" reg="trachomatis">trachomatis</tp:taxon-name-part></tp:taxon-name></italic>, including Spain (35%), France (58%), Netherlands (44.4%), Norway (41.4 %), Denmark (38%), and the United Kingdom (41%).<sup>[13,15,37-39]</sup> Presumably, the wide azithromycin use may account for the high prevalence of macrolide resistance in <italic><tp:taxon-name><tp:taxon-name-part taxon-name-part-type="genus" reg="Mycoplasma">M.</tp:taxon-name-part> <tp:taxon-name-part taxon-name-part-type="species" reg="genitalium">genitalium</tp:taxon-name-part></tp:taxon-name></italic> reported in this study. Additionally, Horner et al. registered recently moderate but convincing evidence that the extended azithromycin regimen for <italic><tp:taxon-name><tp:taxon-name-part taxon-name-part-type="genus" reg="Mycoplasma">M.</tp:taxon-name-part> <tp:taxon-name-part taxon-name-part-type="species" reg="genitalium">genitalium</tp:taxon-name-part></tp:taxon-name></italic> may be more effective than a single dose and is less likely to cause selection of macrolide resistance.<sup>[<xref ref-type="bibr" rid="B40">40</xref>]</sup> This could explain that no selected resistance was found in the present study as all of the eligible participants have received extended dosing of azithromycin.</p>
      <p>Nevertheless, the detected high rate of transmitted macrolide resistance in this study hinders the effective treatment in a significant proportion of individuals. To address this issue, a combined diagnostic-resistance assay has been employed in clinical practice of most European countries.‌<sup>[<xref ref-type="bibr" rid="B41">41</xref>]</sup> The use of these combined tests allows implementation of so called resistance guided therapy, as <italic><tp:taxon-name><tp:taxon-name-part taxon-name-part-type="genus" reg="Mycoplasma">M.</tp:taxon-name-part> <tp:taxon-name-part taxon-name-part-type="species" reg="genitalium">genitalium</tp:taxon-name-part></tp:taxon-name></italic>-positive patients can then be prescribed azithromycin if macrolide susceptible or moxifloxacin if macrolide resistant. Resistance guided therapy is clinically demonstrated to improve patient cure rate and overall patient management, including reduction of time to cure and prevention of ongoing transmission.<sup>[<xref ref-type="bibr" rid="B42">42</xref>,43]</sup> This diagnostic strategy should maintain antimicrobial stewardship, until data on combination therapy and new classes of antimicrobials are available.</p>
      <p>Fortunately, in the present study the efficacy of second-line treatment for <italic><tp:taxon-name><tp:taxon-name-part taxon-name-part-type="genus" reg="Mycoplasma">M.</tp:taxon-name-part> <tp:taxon-name-part taxon-name-part-type="species" reg="genitalium">genitalium</tp:taxon-name-part></tp:taxon-name></italic> infection was 100% and microbiological cure was achieved in all azithromycin failures. Moxifloxacin still has excellent efficacy in Europe<sup>[<xref ref-type="bibr" rid="B44">44</xref>]</sup> although resistance is increasing in Asia-Pacific region with sporadic cases of moxifloxacin failure occurring in Europe<sup>[<xref ref-type="bibr" rid="B45">45</xref>]</sup>. Using moxifloxacin as first-line therapy in all cases of <italic><tp:taxon-name><tp:taxon-name-part taxon-name-part-type="genus" reg="Mycoplasma">M.</tp:taxon-name-part> <tp:taxon-name-part taxon-name-part-type="species" reg="genitalium">genitalium</tp:taxon-name-part></tp:taxon-name></italic> is not recommended because future therapeutic options for multidrug-resistant strains are limited.<sup>[<xref ref-type="bibr" rid="B46">46</xref>]</sup> These options include only doxycycline with poor clinical efficacy and pristinamycin, which is not available in all European countries.</p>
      <p>The impending loss of macrolides, and the emergence and inevitable spread of resistance to fluoroquinolones, first- and second-line recommended agents for <italic><tp:taxon-name><tp:taxon-name-part taxon-name-part-type="genus" reg="Mycoplasma">M.</tp:taxon-name-part> <tp:taxon-name-part taxon-name-part-type="species" reg="genitalium">genitalium</tp:taxon-name-part></tp:taxon-name></italic> in international guidelines<sup>[<xref ref-type="bibr" rid="B6 B7 B8">6–8</xref>]</sup>, clearly necessitates new treatment approaches. While new classes of antimicrobials are urgently needed, antimicrobial combinations for <italic><tp:taxon-name><tp:taxon-name-part taxon-name-part-type="genus" reg="Mycoplasma">M.</tp:taxon-name-part> <tp:taxon-name-part taxon-name-part-type="species" reg="genitalium">genitalium</tp:taxon-name-part></tp:taxon-name></italic> to delay further emergence and spread of antimicrobial resistance, are also being investigated. Recent study demonstrates that &gt;92% of <italic><tp:taxon-name><tp:taxon-name-part taxon-name-part-type="genus" reg="Mycoplasma">M.</tp:taxon-name-part> <tp:taxon-name-part taxon-name-part-type="species" reg="genitalium">genitalium</tp:taxon-name-part></tp:taxon-name></italic> infections can be cured in a population where two-thirds of cases are macrolide resistant and 20% of macrolide-resistant cases are fluoroquinolone resistant.<sup>[<xref ref-type="bibr" rid="B42">42</xref>]</sup> This was achieved with sequential therapy by pretreating with doxycycline and selecting a second antimicrobial with a macrolide-resistance assay. Replacing azithromycin with doxycycline for initial treatment of <italic><tp:taxon-name><tp:taxon-name-part taxon-name-part-type="genus" reg="Mycoplasma">M.</tp:taxon-name-part> <tp:taxon-name-part taxon-name-part-type="species" reg="genitalium">genitalium</tp:taxon-name-part></tp:taxon-name></italic> had the dual advantage of reducing overall use of azithromycin and reducing <italic><tp:taxon-name><tp:taxon-name-part taxon-name-part-type="genus" reg="Mycoplasma">M.</tp:taxon-name-part> <tp:taxon-name-part taxon-name-part-type="species" reg="genitalium">genitalium</tp:taxon-name-part></tp:taxon-name></italic> load.</p>
      <p>The integration of combined molecular-based assays that detect <italic><tp:taxon-name><tp:taxon-name-part taxon-name-part-type="genus" reg="Mycoplasma">M.</tp:taxon-name-part> <tp:taxon-name-part taxon-name-part-type="species" reg="genitalium">genitalium</tp:taxon-name-part></tp:taxon-name></italic>, as well as resistance genes will greatly assist in the delivery of individualized therapy. This diagnostic approach, coupled with use of sequential therapy, is needed to halt the inevitable progression to a multidrug-resistant untreatable <italic><tp:taxon-name><tp:taxon-name-part taxon-name-part-type="genus" reg="Mycoplasma">M.</tp:taxon-name-part> <tp:taxon-name-part taxon-name-part-type="species" reg="genitalium">genitalium</tp:taxon-name-part></tp:taxon-name></italic>.</p>
      <p>This study had several strengths including high recruitment and adherence rates and that all samples were successfully sequenced for macrolide resistance mutations. The main advantages were data availability from Bulgaria and resistance detected in both pre- and post-treatment samples indicating the strong selection induced by extensive antibiotic use. The main limitation was that there were more males in studied cohort and fewer females. This reflects the usually higher male attendance rates to laboratory service and limits evaluation of the contribution of the sex to azithromycin failure.</p>
    </sec>
    <sec sec-type="Conclusions" id="SECID0E5MAE">
      <title>Conclusions</title>
      <p>We report in the present study a high azithromycin failure rate (47.6%) in <italic><tp:taxon-name><tp:taxon-name-part taxon-name-part-type="genus" reg="Mycoplasma">M.</tp:taxon-name-part> <tp:taxon-name-part taxon-name-part-type="species" reg="genitalium">genitalium</tp:taxon-name-part></tp:taxon-name></italic>-infected patients from Bulgaria in association with high levels of pretreatment macrolide resistance. Despite emerging fluoroquinolone resistance in certain regions of the world, during the present investigation moxifloxacin was highly effective in treating azithromycin failures. These findings encourage the use of combined assays for simultaneous detection of <italic><tp:taxon-name><tp:taxon-name-part taxon-name-part-type="genus" reg="Mycoplasma">M.</tp:taxon-name-part> <tp:taxon-name-part taxon-name-part-type="species" reg="genitalium">genitalium</tp:taxon-name-part></tp:taxon-name></italic> and macrolide resistance mutations in order to optimize antimicrobial stewardship and control the selection and spread of resistances. Additionally, this study supports the need to perform antimicrobial resistance surveillance in <italic><tp:taxon-name><tp:taxon-name-part taxon-name-part-type="genus" reg="Mycoplasma">M.</tp:taxon-name-part> <tp:taxon-name-part taxon-name-part-type="species" reg="genitalium">genitalium</tp:taxon-name-part></tp:taxon-name></italic> at local level. In this situation, further investigations on new diagnostic and therapeutic strategies are required to fight against <italic><tp:taxon-name><tp:taxon-name-part taxon-name-part-type="genus" reg="Mycoplasma">M.</tp:taxon-name-part> <tp:taxon-name-part taxon-name-part-type="species" reg="genitalium">genitalium</tp:taxon-name-part></tp:taxon-name></italic> that may soon become untreatable with the appearance of multidrug- resistant strains.</p>
    </sec>
  </body>
  <back>
    <ack>
      <title>Funding</title>
      <p>Supported by research grant DN13/5-15.12.2017, Bulgarian National Science Fund.</p>
    </ack>
    <ref-list>
      <title>References</title>
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