en Medical Bacteriology Medical Bacteriology Original Research Original Research <p><strong>Background: </strong>Human brucellosis is a zoonotic disease caused by Brucella melitensis, Brucella abortus, and Brucella suis. Brucella causes a chronic disease, which subverts the immune defense system of their hosts. In this study, the prevalence of an important Brucella virulence determinant, PrpA, which can modulate immune response, was determined in human isolates.<br> <strong>Methods:</strong> Polymerase chain reaction (PCR) assay was standardized and applied to 37 isolates obtained from patient&rsquo;s specimens. Primers for prpA gene were designed and evaluated using bioinformatic tools. DNA sequencing was performed for further verification.<br> <strong>Results: </strong>In the 37 Brucella isolates (31 Brucella melitensis and 6 Brucella abortus), 32 (86.4%) carried prpA gene.<br> <strong>Conclusion: </strong>Presence of prpA gene in most isolates indicates the high prevalence of this gene among Iranian isolates and emphasizes its role in pathogenicity of this organism.<br> &nbsp;<br> &nbsp;</p> Brucella species, Brucellosis, Proline Racemase, PrpA 332 335 http://mjiri.iums.ac.ir/browse.php?a_code=A-10-3259-1&slc_lang=en&sid=1 Iman Hashemifar Hashemifar.iman@gmail.com 200319475328460033997 200319475328460033997 No Department of Microbiology, School of Medicine, Iran University of Medical Sciences, Tehran, Iran. Faramarz Masjedian Jazi fmasjedian@yahoo.com 200319475328460033998 200319475328460033998 No Department of Microbiology, School of Medicine, Iran University of Medical Sciences, Tehran, Iran. Abbas Yadegar babak_y1983@yahoo.com 200319475328460033999 200319475328460033999 No Foodborne and Waterborne Diseases Research Center, Research Institute for Gastro-enterology and Liver Diseases, Shahid Beheshti University of Medical Sciences, Tehran, Iran. Nour Amirmozafari amirmozafari@yahoo.com 200319475328460034000 200319475328460034000 Yes Department of Microbiology, School of Medicine, Iran University of Medical Sciences, Tehran, Iran.