en باکتری شناسی پزشکی Medical Bacteriology مقاله پژوهشی Original Research Article <p style="text-align: justify;"><span style="font-size:16px;"><span style="font-family:Times New Roman;"><b><span style="background:#1f497d"><span style="color:white"><span style="letter-spacing:-.1pt">Background and Aim:</span></span></span></b><span style="color:black">&nbsp;</span><span style="color:#000000;"><span style="line-height:150%"><i><span style="line-height:150%"><span new="" roman="" times="">Klebsiella (K.) pneumoniae</span></span></i><span style="line-height:150%"><span new="" roman="" times=""> is a major cause of hospital-acquired infections, where biofilm formation and quinolone resistance complicate the treatment outcomes. This research was aimed to examine the biofilm formation occurrence, plasmid-mediated quinolone resistance (PMQR) determinants, and chromosomal alterations among clinical <i>K. pneumoniae</i> isolates.</span></span></span></span><br> <b><span style="background:#1f497d"><span style="color:white"><span style="letter-spacing:-.1pt">Materials and Methods:</span></span></span></b><span style="color:black"> </span><span style="color:#000000;"><span style="line-height:150%"><span style="line-height:150%"><span new="" roman="" times="">In this cross-sectional investigation, 120 unique <i>K. pneumoniae</i> isolates were obtained for evaluation. Antimicrobial susceptibility testing and biofilm production examination were conducted through disk diffusion technique and microtiter plate method, respectively. Minimum inhibitory concentration (MIC) was determined by the agar dilution approach. Polymerase chain reaction (PCR) and DNA sequencing were carried out to identify the resistance- and biofilm-related genes, along with mutations in the <i>gyrA</i> and <i>parC</i> genes.</span></span><span new="" roman="" times=""> The </span><span style="line-height:150%"><span new="" roman="" times="">statistical analysis was performed using SPSS 22.0, and the association between biofilm formation and fluoroquinolones (FQ) resistance was evaluated by Fisher&rsquo;s exact test.</span></span></span></span><span style="color:black"> </span><br> <b><span style="background:#1f497d"><span style="color:white"><span style="letter-spacing:-.1pt">Results:</span></span></span></b><span style="color:black"> </span><span style="color:#000000;"><span style="line-height:150%"><span style="line-height:150%"><span new="" roman="" times="">The highest resistance was observed against ampicillin (77.5%, n=93), highlighting its limited therapeutic effectiveness in clinical settings.</span></span> <span style="line-height:150%"><span new="" roman="" times="">Biofilm production was observed in 69.2% (n=83). Resistance to ciprofloxacin was seen in 56.7% of isolates, and PCR revealed frequent presence of <i>gyrA</i>, <i>parC</i>, <i>qnrS</i>, <i>aac(6&prime;)-Ib-cr</i>, <i>qepA</i>, <i>oqxA</i>, and <i>oqxB</i> genes, with common mutations S83I and D87N in <i>gyrA</i> and S80I and E84V in <i>parC</i>. Biofilm-producing isolates had significantly higher resistance to ampicillin (<i>P</i>=0.001), imipenem (<i>P</i>=0.037), gentamicin (<i>P</i>=0.045), and ceftazidime (<i>P</i>= 0.003), and fluoroquinolone resistance genes (<i>qepA</i>, <i>oqxB</i>) were more prevalent among them.</span></span></span></span><br> <b><span style="background:#1f497d"><span style="color:white"><span style="letter-spacing:-.1pt">Conclusion:</span></span></span></b><span style="color:black">&nbsp;</span><span style="color:#000000;"><span style="line-height:150%"><span style="line-height:150%"><span new="" roman="" times="">This investigation revealed a considerable frequency of PMQR genes and chromosomal alterations in quinolone-resistant <i>K. pneumoniae</i> isolates, highlighting a strong association between biofilm formation and antimicrobial resistance. The outcomes underscore the genetic mechanisms underlying resistance and difficulties in controlling infections triggered by these strains.</span></span></span></span></span></span></p> Biofilm, Klebsiella pneumoniae, PMQR, Quinolone 377 388 http://ijmm.ir/browse.php?a_code=A-10-68-6&slc_lang=en&sid=1 Mohsen Daneshmand m.Daneshmand@mubabol.ac.ir 100319475328460033956 100319475328460033956 No Student Research Committee, Babol University of Medical Sciences, Babol, Iran Masoumeh Kiani M.kianii2018@gmail.com 100319475328460033957 100319475328460033957 No Department of Microbiology, Faculty of Medicine, Shahid Sadoughi University of Medical Sciences, Yazd, Iran Mahlagha Zahedi mahlaghazahedi@gmail.com 100319475328460033958 100319475328460033958 No Department of Pathology, Faculty of Medicine, Shahid Sadoughi University of Medical Sciences, Yazd, Iran Abbas Zare Banadkouki az1171355@gmail.com 100319475328460033959 100319475328460033959 No Department of Microbiology, Shahid Beheshti University, Tehran, Iran Mohammad Hossein Tayefeh-Arbab sh.jamili45@gmail.com 100319475328460033960 100319475328460033960 No Infectious Diseases and Tropical Medicine Research Center, Health Research Institute, Babol University of Medical Sciences, Babol, Iran Abazar Pournajaf abazar_pournajaf@yahoo.com 100319475328460033961 100319475328460033961 Yes Infectious Diseases and Tropical Medicine Research Center, Health Research Institute, Babol University of Medical Sciences, Babol, Iran