en <span style="font-size:9pt"><span style="line-height:normal"><span linotype="" palatino="" style="font-family:"><span style="color:black"><b><span style="font-size:10.0pt"><span cambria="" style="font-family:">Aims:</span></span></b><span style="font-size:10.0pt"><span cambria="" style="font-family:"> Multiple sclerosis is a chronic demyelinating disease that is considered an autoimmune disorder affecting the central nervous system. This study aimed to investigate the pathogenic changes in the natural flora of the mouth in MS patient during different treatment modalities and compare them with healthy individuals.</span></span></span></span></span></span><br> <span style="font-size:9pt"><span style="line-height:normal"><span linotype="" palatino="" style="font-family:"><span style="color:black"><b><span style="font-size:10.0pt"><span cambria="" style="font-family:">Materials & Methods: </span></span></b><span style="font-size:10.0pt"><span cambria="" style="font-family:">120 patients were volunteered and divided into four groups of 30 people: 1) patients with MS taking Natalizumab or Tysabri, 2) patients with MS taking Betaferon, 3) naive MS patients without medications, 4) healthy individuals (control). The changes in oral bacteria (<i>Staphylococcus aureus</i>,<i> Porphyromonas gingivalis</i>,<i> </i>and<i> Bacteroides fragilis</i>) were investigate using real time-PCR.</span></span></span></span></span></span><br> <span style="font-size:9pt"><span style="line-height:normal"><span linotype="" palatino="" style="font-family:"><span style="color:black"><b><span style="font-size:10.0pt"><span cambria="" style="font-family:">Findings: </span></span></b><span style="font-size:10.0pt"><span cambria="" style="font-family:">The prevalence of <i>S. aureus</i> was significantly higher in the Naive MS group (p=0.016), Betaferon group (p=0.001), and Tysabri group (p=0.0001) compared to the healthy group, as well as in Tysabri group compared to the Naive MS group (p=0.005). The prevalence of <i>P. gingivalis</i> was significantly higher in the Betaferon group (p=0.002) and Tysabri group (p=0.0001) compared to the healthy group, as well as in Tysabri group compared to the Naive MS group (p=0.020). The prevalence of <i>B. fragilis</i> was significantly higher in the Naive MS group (p=0.008), Betaferon group (p=0.015), and Tysabri group (p=0.008) compared to the healthy group.</span></span></span></span></span></span><br> <span style="font-size:9pt"><span style="line-height:normal"><span linotype="" palatino="" style="font-family:"><span style="color:black"><b><span style="font-size:10.0pt"><span cambria="" style="font-family:">Conclusion: </span></span></b><span style="font-size:10.0pt"><span cambria="" style="font-family:">Oral bacteria are involved in MS development. Furthermore, MS patients are more susceptible to periodontal disease due to high <i>P. gingivalis</i> presence, and these patients need to receive extra care to prevent periodontal disease.</span></span></span></span></span></span> Multiple Sclerosis,Staphylococcus aureus,Porphyromonas gingivalis,Bacteroides fragilis,Natalizumab (Tysabri),Betaferon, 191 198 http://ijwph.daneshafarand.org/browse.php?a_code=A-10-2061-2&slc_lang=en&sid=3 Z.M. Al-Saadi 1003194753284600379030 1003194753284600379030 Yes Ministry of Health and Environment, Baghdad, Iraq F.D. Al-Aswad 1003194753284600378874 1003194753284600378874 No Department of Oral Medicine, College of Dentistry, Baghdad University, Baghdad, Iraq N.M. Sheaheed 1003194753284600378873 1003194753284600378873 No Neurology Division Baghdad Teaching Hospital Medical City, Baghdad, Iraq