en - باکتری شناسی Bactriology پژوهشي Research <p>-</p> <p style="text-align: justify;"><strong>Backgrounds and Aims:</strong> Mastitis is a mammalian disease which is considered important due to its potential economic damages. <em>Trueperella pyogenes</em>is is one of the important opportunistic pathogens of the mammary glands of cattle. This bacterium can produce acute mastitis infection in dairy cattle. In fact, this bacterium has several virulence genes which contribute to its pathogenicity. Therefore, this study aimed to determine the frequency of this bacterium in the sick cattle in addition to identifying the effective virulence gene in this disease and finally investigating the antibiotic resistance of <em>T. pyogenes.</em></p> <p style="text-align: justify;"><strong>Materials and Methods</strong>: In total, 126 milk samples from mastitic cows, were collected and immediately transferred to the laboratory. Isolation and identification of <em>T. pyogenes</em> strains were performed using bacteriological methods. Moreover, antimicrobial susceptibility testing was performed using the disk diffusion technique polymerase chain reaction was used to detect <em>plo, fimA, fimC, cbpA, nanH</em>, and <em>nanP</em> virulence genes.</p> <p style="text-align: justify;"><strong>Results: </strong><em>T. pyogenes</em> was detected in 46 milk samples. The expression of <em>plo</em> and <em>fimA</em> virulence genes was observed in all samples while fimC expression was detected in 84.7% of cases. The most resistance was observed against tetracycline (97.8%) and gentamicin (86.9%), whereasthe least resistance was reported for chloramphenicol (4.3%) and nitrofurantoin (10.9%).</p> <p style="text-align: justify;"><strong>Conclusions: </strong><em>T. pyogenes</em> has been regarded as one of the bacteria causing mastitis disease in the cattle. <em>Plo, fimA, </em>and<em> fimC</em> virulence genes seem to be the main virulence factors of this bacterium.</p> Antibiotic resistance, Bovine mastitis, Trueperella Pyogenes, Virulence gene 134 141 http://ijml.ssu.ac.ir/browse.php?a_code=A-10-24-2&slc_lang=en&sid=1 Hassan Momtaz Yes Department of Microbiology, Shahrekord Branch, Islamic Azad University, Shahrekord, Iran. Amir Ghafari No Department of Microbiology, Shahrekord Branch, Islamic Azad University, Shahrekord, Iran. Mostafa Sheikh-Samani No Department of Microbiology, Shahrekord Branch, Islamic Azad University, Shahrekord, Iran. Ali Jhazayeri No Department of Microbiology, Shahrekord Branch, Islamic Azad University, Shahrekord, Iran.