结直肠腺瘤患者肠黏膜产肠毒素脆弱拟杆菌和表达pks基因的大肠埃希菌的分布

Expression of enterotoxigenic Bacteroides fragilis and polyketide synthase gene-expressing Escherichia coli in colorectal adenoma patients

目的通过比较结直肠腺瘤患者腺瘤组织、腺瘤旁正常结肠黏膜组织和健康人结肠黏膜组织的总菌、脆弱拟杆菌（BF）、产肠毒素脆弱拟杆菌（ETBF）、表达聚酮合酶（pks）基因的大肠埃希菌（E．coli）（pks＋E．coli）等的差异，了解各细菌在结直肠腺瘤组织、瘤旁组织及正常黏膜组织中分布的差异。方法选取2011年9月至2013年9月于北京大学人民医院消化科经结肠镜检查和病理学诊断确诊为结直肠腺瘤的患者36例，提取36例结肠腺瘤患者的腺瘤组织、腺瘤旁正常结肠黏膜组织和18名健康对照人群的结肠黏膜组织DNA，并对其中总体细菌、BF、ETBF、pks＋Ecoli的含量进行实时荧光定量PCR检测，并分析所测指标与结肠腺瘤发生的联系。结果（1）结肠黏膜中细菌总数在健康人结肠黏膜组织、腺瘤旁正常结肠黏膜组织、腺瘤组织中的含量是依次递减的，中位数分别为：3．18×10^8、1．57×10^8、7．91×10^8拷贝／g组织，3组间及两两间差异均有统计学意义（均P〈0．01）。（2）BF在这3类组织中的含量是依次递减的，中位数分别为：6．03×10^5、4．28×10^4、5．48×10^3拷贝／g组织，3组间及两两间差异均有统计学意义（均P〈0．01）。（3）ETBF分泌的脆弱拟杆菌毒素在这3类组织中的含量是依次递增的，相对表达量分别为1．73±0．30、6．15±1．52、8．54±1．80，其在腺瘤组织中的表达与健康人结肠黏膜组织中的表达差异有统计学意义（P=0．003），而其余两两间比较差异无统计学意义。（4）pks＋E．colipks基因5’端的标记基因clbB在这3类组织中的含量是依次递增的，相对表达量分别为1．06±0．08、2．79±0．19、2．96±0．28，腺瘤组织、腺瘤旁正常结肠黏膜组织中的表达均明显高于健康人结肠黏膜组织（均P〈0．001），腺瘤组织与腺瘤旁正常结肠黏膜组织比较差异无统计学意义。结论结直肠腺瘤患者结肠黏膜中细菌总数明显少于健康人群，但ETBF和pks＋E．coli含量明显高于健康人群。结肠黏膜组织细菌总量及ETBF和pks＋E．coli的含量可能与结直肠腺瘤的发病相关。

[ Abstract] Objective To investigate the distribution of various bacteria in adenoma tissue of coloreetal adenoma （T/CRA）, normal colonic mucosa tissue adjacent to the adenoma （N/CRA）, and healthy colonic mucosa tissue （N/H） by comparing the number of total bacteria, Bacteroides fragilis （ BF）, enterotoxigenic Bacteroides fragilis （ ETBF）, polyketide synthase （ pks ） gene-expressing Escherichia coli （E. coli） （pks ＋ E. coli）among the above 3 types of tissues. Methods A total of 36 patients diagnosed with colorectal adenoma by colonoscopy and pathology in Department of Gastroenterology, Peking University People＇s Hospital from September 2011 to September 2013 were selected into this study. T/CRA and N! CRA tissues from the 36 patients and N/H tissues from 18 healthy controls were collected for DNA extraction. The number of total bacteria, BF, ETBF, pks ＋ E. coli was detected by quantitative real timePCR, and their correlation with colorectal adenoma was analyzed. Results （1） The number of total bacteria decreased gradually from N/H, N/CRA, to T/CRA, with the median values being 3.18 ×10^8 , 1.57 ×10^8 , and 7.91 ×10^7 copies/g, respectively, and with significant difference among the three groups and between each two groups （all P 〈0. 01 ）. （2） The content of BF decreased gradually from N/H, N/ CRA, to T/CRA, the median values being 6. 03 ×10^5 , 4. 28×10^4, and 5.48 ×10^3 copies/g, respectively, and with significant difference among the three groups and between each two groups （ all P 〈 0. 01 ）. （ 3 ） The toxin content produced by ETBF increased from N/H, N/CRA, to T/CRA, the relative expression being 1.73 ±0. 30, 6. 15 ± 1.52, and 8.54 ± 1. 80, respectively. Significant difference was found between the T/ CRA and N/H tissue （P =0. 003）, but not between any other two groups. （4） The expression of clbB in pks＋E, coli was highest in T/CRA colonic tissue （2. 96 ±0. 28）, followed by the N/CRA （2. 79 ±0. 19） and N/H tissue （ 1.06± 0.08 ）. Significant difference was found between T/CRA and N/H tissues, as well as between N/CRA and N/H tissues （ both P 〈 0. 001 ） , but not between T/CRA and N/CRA tissues. Conclusions The number of total bacteria is markedly reduced in the colonic mucosa of CRA patients compared to normal people, while the expressions of ETBF and pks ＋ E. coli are significantly increased. Such changes in total bacterial, ETBF and pks ＋ E. coli concentrations in colonic mucosa may be related to the tumorigenesis of colorectal adenoma.