fa باکتری شناسی Bactriology پژوهشي Research <p><strong>Background and Aims:</strong> The aim of this study was to determine the virulence and antibiotic resistance properties of <em>Streptococcus agalactiae</em> (<em>S.</em> <em>agalactiae</em>) and <em>Streptococcus</em> <em>uberis</em> (<em>S. uberis</em>) isolated from the ruminant&rsquo;s sub-clinical mastitic milk in Iran.</p> <p><strong>Materials and Methods:</strong> Positive samples in the CMT test were cultured and <em>S.</em> <em>agalactiae</em> and <em>S. uberis</em> have been identified using biochemical tests and polymerase chain reaction (PCR). Virulence and antibiotic resistance genes were studied using PCR. A total of 350 milk samples were collected randomly from 4 major provinces of Iran. We chose 55 bovine, 43 ovine, and 32 caprine herds from these regions.</p> <p><strong>Results:</strong> Totally, 34.52% of bovine, 25% of ovine, and 25% of caprine milk samples were found to be contaminated with <em>S. agalactiae </em>and also, 27.38% of bovine, 25% of ovine, and 25% of caprine milk samples were found to be contaminated with <em>S. uberis</em>. The most commonly detected virulence genes of <em>S. agalactiae</em> were <em>cfb </em>(68.75%), <em>scpB</em> and <em>pavA</em> (43.75%). Also, the most commonly detected pathogenic genes of <em>S. uberis</em> were <em>sua</em> and <em>hasB</em> (83.33%), <em>cfu</em> (75.00%) and <em>skc</em> (70.83%). Totally, <em>tetO</em> (89.28%), <em>ermA </em>(82.14%), <em>mefA</em> (73.21%) and <em>tetM</em> (69.64%) were the most common antibiotic resistance genes in <em>Streptococcus</em> isolates. The most resistance were detected against tetracycline (87.5%) and erythromycin (83.92%), respectively.</p> <p><strong>Conclusions:</strong> Our results showed that animal milk samples should be controlled, especially in colder seasons of the year in order to study the presences of <em>S. agalactiae</em> and <em>S. uberis</em>.</p> Antibiotic resistance pattern, Mastitic milk, Streptococcus agalactiae, Streptococcus uberis, Virulence genes 34 47 http://ijml.ssu.ac.ir/browse.php?a_code=A-10-1-42&slc_lang=fa&sid=1 Hassan Momtaz Yes Department of Microbiology, Shahrekord Branch, Islamic Azad University, Shahrekord, Iran. Mahvash eliyasi No Department of Microbiology, Shahrekord Branch, Islamic Azad University, Shahrekord, Iran. Reza Soleimani No Faculty of Veterinary Medicine, Shahrekord Branch, Islamic Azad University, Shahrekord, Iran Ali Jazayeri No Faculty of Veterinary Medicine, Shahrekord Branch, Islamic Azad University, Shahrekord, Iran