Recent studies have proposed that commensal bacteria might be involved in the development and progression of gastrointestinal disorders such as colorectal cancer (CRC). Therefore, in this study, the relative abundance of Fusobacterium nucleatum, Bacteroides fragilis, Streptococcus bovis/gallolyticus, and Enteropathogenic Escherichia coli (EPEC) in CRC tissues, and their association with clinicopathologic characteristics of CRC was investigated in Iranian patients. Moreover, the role of these bacteria in the CRC-associated mutations including PIK3CA, KRAS, and BRAF was studied. To these ends, the noted bacteria were quantified in paired tumors and normal tissue specimens of 30 CRC patients, by TaqMan quantitative Real-Time Polymerase Chain Reaction (qPCR). Next, possible correlations between clinicopathologic factors and mutations in PIK3CA, KRAS, and BRAF genes were analyzed. In studied samples, B. fragilis was the most abundant bacteria that was detected in 66 and 60% of paired tumor and normal samples, respectively. Furthermore, 15% of the B. fragilis-positive patients were infected with Enterotoxigenic B. fragilis (ETBF) in both adenocarcinoma and matched adjacent normal samples. F. nucleatum was also identified in 23% of tumors and 13% of adjacent normal tissue samples. Moreover, the relative abundance of these bacteria determined by 2-ΔCT was significantly higher in CRC samples than in adjacent normal mucosa (p < 0.05). On the other hand, our findings indicated that S. gallolyticus and EPEC, compared to adjacent normal mucosa, were not prevalent in CRC tissues. Finally, our results revealed a correlation between F. nucleatum-positive patients and the KRAS mutation (p = 0.02), while analyses did not show any association between bacteria and mutation in PIK3CA and BRAF genes. The present study is the first report on the analysis of different bacteria in CRC tissue samples of Iranian patients. Our findings revealed that F. nucleatum and B. fragilis might be linked to CRC. However, any link between gut microbiome dysbiosis and CRC remains unknown.

中文翻译：

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伊朗患者结直肠癌与具核梭杆菌和脆弱拟杆菌的关联：初步研究

最近的研究表明，共生细菌可能参与了胃肠道疾病如结直肠癌 (CRC) 的发生和发展。因此，在本研究中，在伊朗患者中调查了 CRC 组织中具核梭杆菌、脆弱拟杆菌、牛链球菌/溶镓和肠致病性大肠杆菌 (EPEC) 的相对丰度及其与 CRC 临床病理特征的关联。此外，研究了这些细菌在包括 PIK3CA、KRAS 和 BRAF 在内的 CRC 相关突变中的作用。为此，通过 TaqMan 定量实时聚合酶链反应 (qPCR)，对 30 名 CRC 患者的配对肿瘤和正常组织标本中的所述细菌进行了定量。接下来，临床病理因素与 PIK3CA、KRAS、和 BRAF 基因进行了分析。在研究的样本中，脆弱拟杆菌是最丰富的细菌，分别在 66% 和 60% 的配对肿瘤和正常样本中检测到。此外，在腺癌和匹配的相邻正常样本中，15% 的脆弱拟杆菌阳性患者感染了产肠毒素的脆弱拟杆菌 (ETBF)。F. nucleatum 在 23% 的肿瘤和 13% 的邻近正常组织样本中也被发现。此外，通过 2-ΔCT 确定的这些细菌的相对丰度在 CRC 样品中显着高于相邻正常粘膜（p < 0.05）。另一方面，我们的研究结果表明，与邻近的正常黏膜相比，S. gallolyticus 和 EPEC 在 CRC 组织中并不普遍。最后，我们的结果揭示了具核梭杆菌阳性患者与 KRAS 突变之间的相关性（p = 0.02），而分析未显示细菌与 PIK3CA 和 BRAF 基因突变之间存在任何关联。本研究是关于伊朗患者结直肠癌组织样本中不同细菌分析的第一份报告。我们的研究结果表明 F. nucleatum 和 B. fragilis 可能与 CRC 相关。然而，肠道微生物群失调与 CRC 之间的任何联系仍然未知。