en باکتری شناسی bacteriology تحقيقي Original Paper <span style="font-size:8pt"><span style="line-height:150%"><span style="tab-stops:53.4pt"><span new="" roman="" style="font-family:" times=""><span style="color:#181717"><b><span style="font-size:12.0pt"><span style="line-height:150%"><span style="color:black">Background: </span></span></span></b><span style="font-size:12.0pt"><span style="line-height:150%"><span style="color:black">The emergence of</span></span></span><span style="font-size:12.0pt"><span style="background:white"><span style="line-height:150%"><span style="color:black"> fluoroquinolones (FQ) resistance in the <em>Escherichia coli</em>&nbsp;(<i>E. coli</i>) sequence type 131 (ST131) has become a major challenge in the management of urinary tract infections (UTI). Chromosomal mutations and plasmid-mediated quinolone resistance (PMQR) determinants</span></span></span></span><span style="font-size:12.0pt"><span style="line-height:150%"><span style="color:black"> <span style="background:white">play an important role in the FQ resistance. </span></span></span></span></span></span></span></span></span><br> <span style="font-size:8pt"><span style="line-height:150%"><span style="tab-stops:177.0pt"><span new="" roman="" style="font-family:" times=""><span style="color:#181717"><b><span style="font-size:12.0pt"><span style="line-height:150%"><span style="color:black">Methods: </span></span></span></b><span style="font-size:12.0pt"><span style="background:white"><span style="line-height:150%"><span style="color:black">This cross-sectional study was conducted in 2020 on 300 urine samples<span class="msoDel" style="text-decoration:line-through"><span style="color:red"><del cite="mailto:AZADE" datetime="2025-03-06T22:39">. </del></span></span>aimed to investigate the prevalence of the chromosomal mutations, the PMQR genes including <i>qnr</i>, <em>aac </em>(<em>6</em>&prime;)-<em>Ib</em>-<em>cr</em><em><span style="font-style:normal">, and efflux </span></em><em>pumps</em><em><span style="font-style:normal"> among the FQ-resistant ST131 and non-ST131</span></em><em> E. coli</em><em> </em></span></span></span></span><span style="font-size:12.0pt"><span style="line-height:150%"><span style="color:black">causing UTI<em><span style="background:white"><span style="font-style:normal">.&nbsp; Initially, the ST131 clone was detected using allele-specific PCR and confirmed by m</span></span></em>ultilocus sequence typing<em><span style="background:white"><span style="font-style:normal">. </span></span></em><span lang="AR-SA" dir="RTL" style="background:white"></span></span></span></span></span></span></span></span></span><br> <span style="font-size:8pt"><span style="line-height:150%"><span style="tab-stops:116.4pt"><span new="" roman="" style="font-family:" times=""><span style="color:#181717"><b><span style="font-size:12.0pt"><span style="line-height:150%"><span style="color:black">Results: &nbsp;</span></span></span></b><span style="font-size:12.0pt"><span style="line-height:150%"><span style="color:black">Among 95 FQ-resistant <i>E. coli</i> isolates, 30% &nbsp;(n=29/95) as belonging to the ST131 clone. The most frequently detected PMQR genes in FQ-resistant isolates were <i>aac(6)&rsquo;-lb-cr</i> and<i> qnr</i>S. However, statistical analysis revealed a stronger association between <i>aac(6ʹ)-Ib-cr</i> and the ST131 clone (62%; p<0.03). The<i> oqx</i>A gene was the most prevalent efflux pump gene observed in both ST131 (n=11; 38%) and non-ST131 (n=16; 24%) isolates. Analysis of the <i>gyr</i>A and <i>par</i>C genes revealed</span></span></span> <span style="font-size:12.0pt"><span style="background:yellow"><span style="line-height:150%"><span style="color:black">significantly higher in ST131 compared to non-ST131</span></span></span></span><span style="font-size:12.0pt"><span style="line-height:150%"><span style="color:black">. Double mutations, S80I+E84V, were significantly more prevalent in both <i>gyr</i>A (76% ST131 vs. 43% non-ST131; p=0.004) and <i>par</i>C (55% ST131 vs. 26% non-ST131; p=0.002). High-level resistance (MIC &ge;32 &mu;g/mL) observed in 96.6% (n=28/29) of ST131 isolates compared to 65% (n=43/66) of non-ST131 </span></span></span><span style="font-size:12.0pt"><span style="line-height:150%"><span style="color:black">isolates. </span></span></span></span></span></span></span></span><br> <span style="font-size:12pt"><span style="line-height:150%"><span new="" roman="" style="font-family:" times=""><strong>Conclusion:</strong> <span style="color:#212121">The double mutations confer high level resistance to FQs in ST131 clone. </span>These findings on resistance mechanisms can guide infection control strategies.<span lang="AR-SA" dir="RTL" style="color:#212121"></span></span></span></span> mutation, plasmid, drug resistance, quinolones, fluoroquinolones 0 0 http://mlj.goums.ac.ir/browse.php?a_code=A-10-1824-1&slc_lang=en&sid=1 Mehdi Bozorgi Mazandarani Mehdibozorgi@yahoo.com 100319475328460032365 100319475328460032365 No Department of Microbiology, Jahrom Branch, Islamic Azad University, Jahrom, Iran Mohammad Kargar microkargar@gmail.com 100319475328460032366 100319475328460032366 Yes Department of Microbiology, Zand Institute of Higher Education, Shiraz, Iran Farshid Kafilzadeh kafilzadeh@jia.ac.ir 100319475328460032367 100319475328460032367 No Department of Microbiology, Jahrom Branch, Islamic Azad University, Jahrom, Iran