en باکتری شناسی پزشکی Medical Bacteriology مقاله پژوهشی Original Research Article <p style="text-align: justify;"><span style="font-family:Times New Roman;"><span style="font-size:16px;"><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"> </span><i>Serratia marcescens</i> (<i>S. marcescens</i>) is a Gram-negative, facultative anaerobic bacterium belonging to the Serratia genus of clinical importance. It is an opportunistic pathogen associated with various human infections, including pneumonia, meningitis, wound and burn infections, respiratory tract infections, urinary tract infections, bacteremia, and eye infections. The purpose of this study was to assess the frequency of <i>S. marcescens</i> in different clinical infections and evaluate the major virulence genes responsible for its pathogenicity.<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>Clinical specimens (n=200) were collected from urinary, wound, burn, and eye infections from patients referred to Al-Diwaniyah Teaching Hospital and private clinics of Al-Diwaniyah Governorate from March 11 to August 20, 2024. Bacterial isolates were initially identified by cultural, microscopic, and biochemical examinations and confirmed by the VITEK system. Molecular characterization was done by PCR amplification of <i>PhlA</i>, <i>ShlA</i>, and <i>FlhD </i>virulence genes. The 16S rRNA gene was identified as control. The validated isolates were deposited in NCBI GenBank.<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>Twenty <i>S. marcescens</i> isolates were obtained from 200 samples: 15 (75%) from urinary tract infections, 3 (15%) from wounds and burns, and 2 (10%) from eye infections. The <i>FlhD</i>,<i> PhlA</i> and <i>ShlA</i> genes were found in 100%, 80%, and 35% of the isolates.<br> <b><span style="background:#1f497d"><span style="color:white"><span style="letter-spacing:-.1pt">Conclusion:</span></span></span></b><span style="color:black"> </span>The study emphasized that identification of major virulence determinants such as <i>FlhD</i>, <i>PhlA</i>, and <i>ShlA </i>enhances our understanding of <i>S. marcescens</i> pathogenicity in the studied region and provides a molecular basis for future epidemiological and clinical research.</span></span></p> FlhD, PhlA, Serratia marcescens, ShlA, Virulence Genes 127 139 http://ijmm.ir/browse.php?a_code=A-10-2759-1&slc_lang=en&sid=1 Aintizar Jabir Kazar Aintizar.Kazar@qu.edu.iq 100319475328460031764 0009-0007-7941-9160 No Department of Biology, College of Education, University of Al-Qadisiyah, Al-Diwaniyah, Iraq Azhar Noory Hussein azhar.almousawi@qu.edu.iq 100319475328460031765 100319475328460031765 Yes Department of Biology, College of Education, University of Al-Qadisiyah, Al-Diwaniyah, Iraq