en باکتری شناسی bacteriology تحقيقي Original Paper <div style="text-align: justify;"><span style="font-family:Times New Roman;"><span style="font-size:12px;"><b>Background:</b> The emergence of fluoroquinolone (FQ) resistance in the <i>Escherichia coli</i> (<i>E. coli</i>) sequence type 131 (ST131) clone has become a major challenge in the management of urinary tract infections (UTIs). Chromosomal mutations and plasmid-mediated quinolone resistance (PMQR) determinants play an important role in FQ resistance.<br> <b>Methods:</b> This cross-sectional study was conducted in 2020 on 300 urine samples. It aimed to investigate the prevalence of chromosomal mutations, PMQR genes, including <i>qnr</i> and <i>aac </i>(<i>6&prime;</i>)<i>-Ib-cr</i>, and efflux pumps among FQ-resistant ST131 and non-ST131 <i>E. coli</i> causing UTIs. Initially, the ST131 clone was detected using allele-specific PCR and confirmed by Multilocus Sequence Typing.<br> <b>Results:</b> Among 95 FQ-resistant <i>E. coli</i> isolates, 29 (30%) belonged to the ST131 clone. The most frequently detected PMQR genes in FQ-resistant isolates were <i>aac </i>(<i>6&prime;</i>)<i>-Ib-cr</i> and <i>qnrS</i>. However, statistical analysis revealed a stronger association between <i>aac </i>(<i>6&prime;</i>)<i>-Ib-cr</i> and the ST131 clone (62%; p < 0.03). The <i>oqxA</i> 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>gyrA</i> and <i>parC</i> genes revealed a significantly higher frequency of mutations in ST131 compared with non-ST131. Double mutations, S80I + E84V, were significantly more prevalent in both <i>gyrA</i> (76% ST131 vs. 43% non-ST131; p = 0.004) and <i>parC</i> (55% ST131 vs. 26% non-ST131; p = 0.002). Notably, the substitution E84G was exclusive to non-ST131 isolates (n = 4). High-level resistance (MIC &ge; 32 &mu;g/mL) was observed in 96.6% (28/29) of ST131 isolates compared with 65% (43/66) of non-ST131 isolates.<br> <b>Conclusion</b>: The double mutations confer high-level resistance to FQs in the ST131 clone. These findings regarding resistance mechanisms can guide infection control strategies.</span></span></div> <br> <span style="font-size:12pt"><span style="line-height:150%"><span new="" roman="" style="font-family:" times=""><span lang="AR-SA" dir="RTL" style="color:#212121"></span></span></span></span> Mutation, Plasmids, 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, 100319475328460032601 100319475328460032601 No Department of Microbiology, Ja.C., Islamic Azad University, Jahrom, Iran Mohammad Kargar microkargar@gmail.com 100319475328460032602 100319475328460032602 Yes Department of Microbiology, Zand Institute of Higher Education, Shiraz, Iran Farshid Kafilzadeh kafilzadeh@jia.ac.ir 100319475328460032603 100319475328460032603 No Department of Microbiology, Ja.C., Islamic Azad University, Jahrom, Iran