en Molecular Microbiology Molecular Microbiology مقاله کامل Full Length/Original Article <span style="font-size:12px;"><span style="font-family:Times New Roman;"><span style="line-height:normal"><span calibri=""><b><span lang="EN-GB" style="color:black">Background: </span></b><span lang="EN-GB" style="color:black">The presence of microbiome in the blood samples of healthy individuals has been addressed. However, no information can be found on the healthy human blood microbiome of Iranian subjects. The current study is thus aimed to investigate the existence of bacteria or bacterial DNA in healthy individuals.</span></span></span><br> <span style="line-height:normal"><span calibri=""><b><span lang="EN-GB" style="color:black">Methods: </span></b><span lang="EN-GB" style="color:black">Blood samples of healthy subjects were incubated in BHI broth at 37 &deg;C for 72 h. The 16S rRNA PCR and sequencing were performed to analyze bacterial isolates. The 16S rRNA PCR was directly carried out on DNA samples extracted from the blood of healthy individuals. </span><span style="color:black">Next generation sequencing (NGS) was conducted on blood samples with culture-positive results.</span></span></span><br> <span style="line-height:normal"><span calibri=""><b>Results: </b>Fifty blood samples were tested, and six samples were positive by culture as confirmed by Gram staining and microscopy. The obtained 16S rRNA sequences of cultured bacterial isolates revealed the presence of <i>Bacilli</i> and <i>Staphylococcus</i> species by clustering in the GeneBank database (&ge;97% identity). <span style="color:#131413">The 16S rRNA gene sequencing results of one non-cultured blood specimen showed the presence of <i>Burkholderia</i>. NGS results illustrated the presence of </span><i>Romboutsia</i>, <i>Lactobacillus</i>,<i> Streptococcus</i>,<i> Bacteroides, </i>and<i> Staphylococcus </i>in the blood samples of positive cultures.</span></span><br> <span style="line-height:normal"><span calibri=""><strong><span calibri="">Conclusion:</span></strong> The dormant blood microbiome <span style="color:#131413">of healthy individuals may give the idea that the steady transfer of bacteria into the blood does not&nbsp;necessarily lead to sepsis.</span> However, the origins and identities of blood-associated bacterial rDNA sequences need more evaluation in the healthy population.</span></span><br> &nbsp;</span></span> Bacteria, Blood, Microbiome, Sequencing, 16S rRNA 230 239 http://ibj.pasteur.ac.ir/browse.php?a_code=A-10-54-4&slc_lang=en&sid=1 Javad Raeisi javadraeisi39@yahoo.com 0000-0002-0081-2143 No Department of Microbiology, Qom Branch, Islamic Azad University, Qom, Iran Mana Oloomi manaoloomi@yahoo.com 0000-0002-4723-5021 Yes Department of Molecular Biology, Pasteur Institute of Iran, Tehran, Iran Mohammad Reza Zolfaghari* mreza.zolfaghary@gmail.com 0000-0001-5291-3627 No Department of Microbiology, Qom Branch, Islamic Azad University, Qom, Iran Seyed Davar Siadat d.siadat@gmail.com 0000-0002-6892-5603 No Department of Mycobacteriology, Pasteur Institute of Iran, Tehran, Iran Mohsen Zargar zargar@qom-iau.ac.ir 0000-0002-3108-5655 No Department of Microbiology, Qom Branch, Islamic Azad University, Qom, Iran Zahra Pourramezan z.pourramezan@gmail.com 0000-0002-4591-7248 No Department of Molecular Biology, Pasteur Institute of Iran, Tehran, Iran