en Diagnostic/screening methods and protocols Diagnostic/screening methods and protocols Original article Original article <p dir="ltr"><strong>Introduction:</strong> Toxigenic <em>Clostridium difficile</em> is the major cause of antibiotic-associated diarrhea, colitis, and pseudomembranous colitis. The pathogenicity of <em>C. difficile </em>is related to toxins A&B. Children with cancer are at risk of developing <em>C. difficile</em> infection (CDI) due to increased exposure to antibiotics, immunosuppression, and longer hospital stays. Recently, due to higher sensitivity and specificity of nucleic acid amplification test (NAATs) compared to toxin enzyme immunoassays (EIAs), many laboratories are transitioning to NAATs for detection of CDI. We aimed to use a multiplex PCR to detect the <em>C. difficile </em>toxin genes <em>tcdA</em>, <em>tcdB</em> and <em>tpi</em> in stool of cancerous children. We also aimed to show the effects of chemotherapy regimens on the prevalence of <em>C. difficile</em> in these children. <strong>Methods:</strong> 105 fecal samples were collected from cancerous children who were hospitalized and undergoing chemotherapy. The presence of <em>tcdA, tcdB</em>, and <em>tpi</em> genes were tested. <strong>Results:</strong> <em>C. difficile</em> was identified in 17.14% of children and the detection rate of A^-B⁺ strains was higher than A⁺B⁺ and A⁺B^- strains. <em>C. difficile </em>was found in 17.8% of children who received single antibiotic (5/28 cases virulence genes were detected in 4 cases) and in 41.4% of patients who received more than one antibiotics (12/29 cases virulence genes were detected in 8 cases<strong><span dir="RTL">﴿</span></strong>. <strong>Conclusion:</strong> Multiplex PCR is a powerful technique for preliminary screening and rapid detection of <em>C. difficile</em> and its virulence genes in the stool of cancerous children. The prevalence of <em>C. difficile </em>in cases receiving several antibiotics was higher than those receiving single antibiotics.</p> Antibiotic Prophylaxis, Cancer, Toxigenic, Clostridium difficile, Multiplex PCR 95 99 http://jommid.pasteur.ac.ir/browse.php?a_code=A-10-51-1&slc_lang=en&sid=1 Hadis Tavafi hadistavafi@yahoo.com No Department of Biology, Faculty of Sciences, Shahed University, Tehran, Iran Parviz Owlia owlia@yahoo.com No Molecular Microbiology Research Center, Shahed University, Tehran, Iran Fariba Shirvani shirvanifariba@rocketmail.com No Pediatric Infections Research Center, Mofid Children Hospital, Tehran, Iran Mozhgan Hashemie Hashemie@yahoo.com No Pediatric Infections Research Center, Mofid Children Hospital, Tehran, Iran Nader Shahrokhi shahrokhi@pasteur.ac.ir Yes Department of Molecular Biology, Pasteur Institute of Iran, Tehran, Iran