en میکروب شناسی Microbiology مقالات اصلی Original Article <div style="text-align: justify;"><strong><em>Background: </em></strong>One of the causes of male infertility is Genital tract infections (GTI). Considering the&nbsp;importance of GTI, widespread recognition of them seems necessary. we aimed to characterize and compare&nbsp;semen microbial populations in fertile and infertile men who referred to an infertility clinic in Yazd, Iran.&nbsp;<br> <br> <em><strong>Methods: </strong></em>Semen samples were collected from two groups of fertile (268) and infertile (210) men.&nbsp;Sperm analysis (concentration, morphology, viability and motility parameters) were performed&nbsp;according to the World Health Organization (WHO) 2010 guidelines laboratory manual. Bacterial&nbsp;isolation was performed in Sheep Blood Agar and Eosin Methylene Blue (EMB) agar plates. For&nbsp;PCR, samples were analyzed with genus specific primers.<br> <br> <strong><em>Results: </em></strong>All semen characteristics were poor in the infertile group compared to those in the fertile men&nbsp;(p-value< 0.05). Enterococcus spp. (18.7%, 17.1%; p= 0.814), E. coli (7.9%, 11.4%; p= 0.486),&nbsp;Staphylococcus aureus (6.4%, 2.9%; p= 0.398) and Proteus mirabilis (0%, 2.9%; p= 0.002) were the most<br> common agents, respectively. Also, the results obtained from PCR were confirmed using culture-base&nbsp;method.<br> <br> <em><strong>Conclusions:</strong></em> Proteus mirabilis contamination was identified in the infertile group. While no&nbsp;significant association was observed between male infertility and semen microbial populations, p.&nbsp;mirabilis may be the leading cause of reproduction impairment in men.</div> Infertility, Microbial contamination, culture, PCR. 402 411 http://rbmb.net/browse.php?a_code=A-10-693-1&slc_lang=en&sid=1 Alireza Torki 100319475328460012584 100319475328460012584 No Department of Microbiology, School of Medicine, Iran University of Medical Sciences, Tehran, Iran & Department of Microbiology, School of Medicine, Shahid Sadoughi University of Medical Sciences, Yazd, Iran. Nour Amirmozafari amirmozafari@iums.ac.ir. 100319475328460012585 100319475328460012585 Yes Department of Microbiology, School of Medicine, Iran University of Medical Sciences, Tehran, Iran. Malihe Talebi 100319475328460012586 100319475328460012586 No Department of Microbiology, School of Medicine, Iran University of Medical Sciences, Tehran, Iran. Alireza Talebi 100319475328460012587 100319475328460012587 No Andrology Research Center, Yazd Reproductive Sciences Institute, Shahid Sadoughi University of Medical Sciences, Yazd, Iran.