中文摘要：

目的利用16S r DNA PCR及变性梯度凝胶电泳（DGGE）技术,探讨生后经验性应用抗生素对早产儿早期肠道菌群的影响。方法以2014年1月至2015年1月在重庆医科大学附属儿童医院住院治疗的早产儿为研究对象,使用哌拉西林-他唑巴坦〉7 d为哌拉西林组,7 d内未使用抗生素为对照组。收集胎粪（〈12 h）和3、5、7日龄（d3、d5、d7）的粪便标本,采用PCR-DGGE方法对肠道菌群的变化行动态观察,同时行克隆测序分析菌群组成的变化。结果 24例早产儿的96份粪便标本进入分析,哌拉西林组和对照组各12例,两组基线具可比性。24份胎粪提取细菌DNA后行PCR扩增失败,未行DGGE分析。1哌拉西林组d3、d5、d7时点的Shannon指数中位数（P25-P75）分别为1.64（1.16-1.92）、1.97（1.69-2.20）和1.22（0.69-2.10）;对照组分别为1.39（0.94-1.94）、2.24（2.07-2.49）和2.38（2.07-2.61）,哌拉西林组d7时点的Shannon指数显著低于对照组（P〈0.05）。2随日龄增加,对照组Shannon指数逐渐升高;哌拉西林组Shannon指数呈降低趋势。3d7时点哌拉西林组和对照组均以克雷伯菌属占绝对优势（35.5%和42.4%）,且乳酸杆菌属检出率均较低（1.6%和0.8%）。哌拉西林组较对照组肠球菌属（21.0%vs 7.2%）及链球菌属（25.8%vs 4.0%）比例明显增加,肠杆菌比例明显降低（3.2%vs 12.8%）。结论早产儿菌群结构简单,生后抗生素应用会降低肠道菌群多样性。

英文摘要：

Objective To analyze the effect of empirical antibiotic therapy on the intestinal microbiota of preterm infants and its dynamic change by 16 S r DNA PCR-denaturing gradient gel electrophoresis（ DGGE）. Methods In the period from January 2014 to January 2015,twenty-four hospitalized preterm infants in Children＇ s Hospital of Chongqing Medical University were enrolled and divided into piperacillin-tazobactam treatment（ PT） group and antibiotic free（ AF） group. The meconium and fecal samples on d3,d5 and d7 were collected during the first week of life. After DNA extraction and PCR amplification,the microbial community diversity was analyzed through DGGE fingerprints. The distributions of common dominant bacteria were investigated by TA cloning and sequencing. Results A total of 96 fecal samples were analyzed. The amplification of bacterial DNA from 24 meconium（ 12 h）was failed and DGGE analysis was not performed. 1The median（ P25- P75） of Shannon index of PT group on d3,5 and 7 was 1.64（ 1. 16- 1. 92） 、1. 97（ 1. 69- 2. 20） and 1. 22（ 0. 69- 2. 1） respectively,and that of AF group at the same time point was 1.39（ 0. 94- 1. 94） 、2. 24（ 2. 07- 2. 49） and 2. 38（ 2. 07- 2. 61）. On d3 and d5 of postnatal life,PT and AF infants did not differ in the diversity index of the fecal bacterial community,but on d7,the Shannon index of PT group was significantly lower than that of the AF group（ P〈0. 05）. 2 The result of DGGE at all the 3 time points showed that the Shannon index of AF group gradually increased during the first week of life,while the Shannon index of PT group had a tendency of decrease. 3The bacterial composition on day 7 from DGGE fingerprint showed that Klebsiella sp. was dominant（ 35. 5% and 42. 4%） and the proportion of lactobacillus sp. was low（ 1. 6% and 0. 8%） in both groups. The proportions of Enterococcus sp. and Streptococcus sp. in PT group were higher（ 21. 0% vs 7. 2%,25. 8% vs 4. 0%）,while the proportion of Enterobacter sp. was lower t