妊娠期糖尿病对母乳喂养的12周龄婴儿肠道菌群影响

目的 比较妊娠期糖尿病（GDM）及正常孕妇的持续母乳喂养的12周龄婴儿肠道菌群的分布特点,以探索GDM对12周龄婴儿肠道菌群的影响。方法 选择2016年6月—2019年12月入组的母亲及其随访至12周龄的母乳喂养的婴儿,依据母亲孕期血糖检测结果将母乳喂养婴儿分为GDM组（n=13）和对照组(n=27)。采集婴儿12周龄粪便,采用16S rDNA高通量测序技术对所有粪便样本进行检测,比较两组肠道菌群分布特点。采用Spearman相关分析法分析肠道菌群与孕期血糖、婴儿体重的相关性。结果 共纳入40对研究对象,GDM组13对,对照组27对。两组的优势菌门均为放线菌门、厚壁菌门和变形菌门,GDM组的疣微菌门相对丰度高于对照组,差异有统计学意义（Z=2.233,P <0.05）。在属水平上,GDM组中肠道菌群优势菌属来自放线菌门和厚壁菌门,对照组中肠道菌群的优势菌属来自放线菌门、厚壁菌门和变形菌门。LEfSe差异分析结果显示,GDM组中疣微菌门/目/科、阿克曼氏菌、劳森氏菌、哈利真杆菌的丰度明显升高（LDA>2）,而在对照组中芽孢杆菌目、孪生球菌属、丹毒梭菌属的丰度明显升高（LDA&...     

婴儿肠道菌群的形成及其与食物过敏的关系

目的　观察健康婴儿肠道菌群的定植过程及其在食物过敏症患儿的变化 ,分析肠道菌群形成与婴幼儿食物过敏的相互关系。方法　采用荧光定量PCR技术测定细菌 16SrRNA ,经与标准曲线对照计算细菌数量 ,对 71例健康无过敏症母乳喂养婴儿和 10 0例食物过敏婴儿粪便乳酸杆菌、双歧杆菌和大肠杆菌行定量检测。结果　婴儿肠道菌群处于动态定植过程 ,随生长发育 ,双歧杆菌和乳酸杆菌在肠道定植增加 ,大肠杆菌数量减少。食物过敏婴幼儿肠道乳酸杆菌、双歧杆菌数量较健康婴幼儿低 ,而大肠杆菌数量较健康婴幼儿高。结论　婴儿期肠道菌群仍处于动态演替过程。食物过敏婴儿肠道菌群与健康婴儿不同     

婴儿肠道菌群形成与喂哺方式及食物过敏的关系

目的观察健康婴儿在不同喂养方式下肠道菌群的定植过程及其在食物过敏时的变化,分析肠道菌群形成与婴幼儿食物过敏的相互关系及母乳喂养的意义。方法采用荧光定量PCR技术测定细菌16SrRNA,对健康无过敏症131例(其中母乳喂养71例,人工喂养60例)及100例过敏症婴儿粪便中乳酸杆菌、双歧杆菌和大肠杆菌进行定量检测。结果婴儿肠道菌群处于动态定植过程。母乳喂养婴儿肠道乳酸杆菌、双歧杆菌数量较人工喂养婴儿高(P<0.05),而大肠杆菌数量较人工喂养婴儿低(P<0.05)。食物过敏婴幼儿肠道乳酸杆菌、双歧杆菌数量较健康婴幼儿低(P<0.05),而大肠杆菌数量较健康婴幼儿高(P<0.05)。结论婴儿期肠道菌群处于动态演替过程。不同的喂养方式对肠道菌群有影响,过敏性疾病婴儿肠道菌群与健康婴幼儿不同,应大力提倡母乳喂养。     

动态监测婴儿肠道16SrDNA宏基因组5例报告

目的 探讨婴儿肠道16S rDNA 宏基因组的动态变化.方法 收集5 例健康婴儿生后3 d、1 个月、6 个月、1 岁时粪便样本共17 份,提取细菌总DNA,采用新一代高通量测序技术对16S rDNA 的V6 高变区测序并进行物种分类、丰度及多样性分析.结果 17 份样品共产生原始测序数据为2 190.66 Mbp,Operational Taxonomic Units(OTU)数量36~308;优势菌门包括变形菌门、厚壁菌门、拟杆菌门和放线菌门;不同婴儿间肠道菌群分布有差异;科水平>1% 的物种生后3 d 时2~4 种,1 个月、6 个月时增至最多7 种,1 岁时达10 种;4 个时间点的npShannon 和Simpson 指数均值分别为1.117、1.460、2.088、2.50 和0.443、0.408、0.229、0.143.结论 婴儿粪便中含丰富细菌基因组;细菌物种丰度及分类存在个体差异;细菌多样性随日龄而增加,婴儿肠道菌群结构出生后逐渐趋向复杂和多样.     

婴儿肠道菌群与分娩方式、喂养方式及胆汁淤积性肝病的关系

目的分析分娩方式和喂养方式对健康婴儿肠道菌群的影响,探讨肠道相关分子微生态在胆汁淤积性肝病中的作用及意义。方法收集37例健康婴儿(其中阴道分娩21例,剖宫产16例;母乳喂养15例,人工喂养22例)及84例胆汁淤积性肝病婴儿粪便,提取粪便中细菌DNA并测量A260值;应用实时荧光定量PCR反应测定粪便中双歧杆菌、乳酸杆菌及大肠杆菌3种代表菌的数量。结果阴道分娩婴儿与剖宫产婴儿比较,母乳喂养婴儿与人工喂养婴儿比较,粪便标本中细菌DNA A260值和3种代表菌数量差异均无统计学意义(Pa>0.05)。健康对照组与胆汁淤积性肝病组粪便标本中细菌的DNA A260值分别为(1.94±0.47)g.L-1和(0.40±0.09)g.L-1,2组比较差异有统计学意义(t=8.91,P=0.00);健康对照组与胆汁淤积性肝病组3种细菌数(lg拷贝数/g湿便)的对数值比较差异均有统计学意义(双歧杆菌9.49±0.59 vs 7.68±0.57;t=15.96,P=0.00;乳酸杆菌8.58±0.32 vs 8.16±0.70;t=3.46,P=0.00;大肠杆菌6.87±0.67 vs 7.26±0.86;t=-2.41,P=0.02)。结论不同的分娩方式、喂养方式对婴儿期肠道菌群无影响;胆汁淤积性肝病婴儿肠道菌群与健康婴儿不同,粪便中细菌总量减少,双歧杆菌及乳酸杆菌数量明显减少,大肠杆菌的数量则明显增多,提示肠道菌群失调与婴儿胆汁淤积性肝病的发生、发展有一定关系。     

新生儿肠道微生态学研究现况

在人的肠道中栖息着大约 1× 10 14个、约 10 0多种细菌 ,构成了所谓肠内菌群 ,其中肠杆菌、肠球菌等需氧菌仅占菌群的 1/ 10 0 0 ,绝大多数为厌氧菌 ,健康情况下它们与宿主之间处于生理的、和谐的、相互依赖、相互制约的状态 ,维持人体肠道的微生态平衡 ,对保证人体健康有着重要意义。1　新生儿肠道正常菌群的定植过程新生儿刚出生时胎粪是无菌的 ,生后数小时粪便中首先出现肠球菌、链球菌和肠杆菌等需氧或兼性厌氧菌。生后2 4ｈ大肠杆菌占优势 ;双歧杆菌于生后第 2天出现 ,增长十分迅速 ,第 4～ 5天开始占优势 ,1周后其数量可达细菌总数的…     

不同分娩方式对母乳喂养婴儿肠道菌群的影响

目的新生儿出生后其肠道立即被来自母体和周围环境中的微生物定植,许多研究表明,消化道早期定植的肠道菌群在婴儿免疫系统的发育过程中起重要的作用。该研究探讨了分娩方式对母乳喂养婴儿肠道菌群和粪便性状的影响。方法以60例40～47日龄的健康足月母乳喂养婴儿为观察对象,按分娩方式分为自然分娩组和剖宫产组(n=30)。在6、8、10、12周龄采集婴儿粪便标本,并同时记录婴儿体质量、头围及粪便性状。应用实时荧光定量PCR技术对婴儿肠道乳酸杆菌属、双歧杆菌属及双歧杆菌亚种(长双歧杆菌和短双歧杆菌)进行定量检测。结果剖宫产娩出的婴儿肠道乳酸杆菌和长双歧杆菌数量低于自然分娩组(P<0.05);自然分娩的婴儿粪便pH值低于剖宫产组(6.2对6.9,P﹤0.05);分娩方式对粪便性状和婴儿的生长发育无影响。结论剖宫产降低母乳喂养婴儿肠道乳酸杆菌和双歧杆菌的水平。     

Features of intestinal flora in children with food protein-induced proctocolitis based on high-throughput sequencing北大核心CSCD

目的 通过高通量测序分析食物蛋白诱导性直肠结肠炎（food protein-induced proctocolitis，FPIP）患儿肠道菌群特征。 方法 选取2018年10月至2021年2月遵义医科大学第三附属医院门诊就诊的小于6月龄纯母乳喂养发生FPIP患儿31例纳入FPIP组，正常健康婴儿31例纳入健康对照组；采集两组粪便样本提取DNA并通过PCR扩增，采用高通量测序分析粪便样品中的16S rDNA V3~V4片段并进行相关生物信息学分析。 结果 肠道菌群多样性分析示FPIP组菌群多样性Shannon指数低于健康对照组，但差异无统计学意义（P>0.05）；菌群丰富度Chao指数高于健康对照组（P<0.01）。在门水平上，两组菌群组成均主要由厚壁菌门、放线菌门、变形菌门、拟杆菌门4个菌门构成；与健康对照组相比，FPIP组中放线菌门构成比显著降低（P<0.001），变形菌门构成比明显增加（P<0.05）。在属水平上，FPIP组主要由大肠埃希氏菌属、梭状芽孢杆菌属、肠球菌属、克雷伯氏菌属和双歧杆菌属组成；健康对照组主要由双歧杆菌属、链球菌属组成；与健康对照组相比，FPIP组中双歧杆菌属和瘤胃球菌属构成比明显降低（P<0.05），梭状芽孢杆菌属和志贺氏菌属构成比明显增加（P<0.05）。 结论 FPIP组与健康对照组相比，肠道菌群多样性下降，丰富度升高；在菌群组成结构上某些细菌菌属存在差异。提示在FPIP的发生发展过程中，肠道微生物群在属水平上的构成改变可能起到了重要作用。     

儿童幽门螺杆菌根除治疗过程中肠道菌群的变化

目的探讨儿童幽门螺杆菌根除治疗对肠道菌群的影响,并寻找影响根除治疗效果的差异菌群。方法确诊幽门螺杆菌感染儿童进行三联标准化方案治疗14天,留取治疗前、治疗7天及14天时的粪便进行16SrDNA测序。根据取样时间分为治疗前组、治疗7天组、治疗14天组,根据治疗效果分为治疗成功组、治疗失败组,根据既往根治病史分为复治成功组、初治成功组,分析不同组别之间的菌群差异。结果幽门螺杆菌感染儿童肠道菌群优势菌门依次为厚壁菌门、拟杆菌门、变形菌门、放线菌门、疣微菌门,主要优势菌属有拟杆菌、栖粪杆菌、大肠杆菌/志贺菌、双歧杆菌、Gemmiger、克雷伯菌。与治疗成功组相比,普氏菌属在治疗失败组相对丰度升高,差异有统计学意义(P0.001)。幽门螺杆菌根除治疗前、治疗7天和14天比较,各肠道菌群相对丰度均发生改变,差异有统计学意义(P0.05)。LEfSe分析及组间秩和检验发现,治疗失败组弓形杆菌属、肠道巴恩斯菌属、Coprobacter、粪球菌属、霍尔德曼菌属、假单胞菌属高于治疗成功组,差异有统计学意义(LDA2)。与初治成功组相比,复治成功组不动杆菌属、魏斯菌属、萨特菌属、普罗维登斯菌属显著升高(LDA2),另枝菌属、丹毒丝菌属、梭状芽胞杆菌属、粪杆菌属、Gemmiger显著降低(LDA2)。结论幽门螺杆菌根除治疗影响肠道菌群结构,表现为菌群多样性下降及优势菌群改变。肠道致病性细菌的生长可能影响幽门螺杆菌根除效果,导致根除治疗失败。     

婴儿早期肠道双歧杆菌构建规律的初探

目的 通过系统分析婴儿早期肠道双歧杆菌种群动态变化,初步探索婴儿肠道8 种双歧杆菌构建的规律。方法 收集2013 年3~4 月间16 例正常足月新生儿第1 次、第2、4、7、10、14、28、90 天的粪便,培养分离粪便中双歧杆菌;使用PCR 对分离菌株进行双歧杆菌属及其8 个种水平的鉴定。结果 从受试婴儿粪便中共检出优势双歧杆菌152 株,以B. breve 的检出率(22.4%)最高;第4 天开始在新生儿肠道检出双歧杆菌,定植率为8%;第7 天后双歧杆菌定植率迅速上升,至第28 天和3 月龄时定植率分别达到54% 和60%,均显著高于生后第4 天(均P<0.05)。第10 天时婴儿肠道已有成人型双歧杆菌B. catenulatum 定植,第14 天时检测到婴儿型双歧杆菌B. infantis 定植;至3 月龄时才在婴儿粪便中检测到高水平的婴儿型双歧杆菌B. infantis,且大部分婴儿肠道双歧杆菌种类总数不超过2 种。结论 本研究受试婴儿早期肠道双歧杆菌的多样性偏低,婴儿型双歧杆菌出现偏迟,相反成人型双歧杆菌发现较早。     

Establishment of the gut microbiota in Western infants

In adult individuals, the intestinal microbiota comprises several hundred, mostly anaerobic, bacterial species. This complex ecosystem is formed through the successive establishment of different bacteria in infancy and early childhood. Facultative and aerotolerant bacteria establish first, followed by more and more strict anaerobes. The bacteria derive from different sources and the colonization pattern is influenced by delivery mode and environmental factors. Commensal microbes provide the major drive for maturation of the immune system. Increased hygiene appears to have changed the gut flora of Western infants, which may affect the risk of developing immune mediated diseases.
Conclusion: It is clear that the process of infant colonization needs to be studied further, since composition of the microbiota may impact on child health.     

Intestinal microflora in early infancy: composition and development

The neonatal intestinal microbiota is a complex ecosystem composed of numerous genera, species and strains of bacteria. This enormous cell mass performs a variety of unique activities that affect both the colonic and systemic physiology. Its primary activities include nutritive, metabolic, immunological and protective functions. Most studies of infants have been based on faecal samples using the classical plating techniques with culturing on specific media. The limitations of these methods must be taken into account when evaluating the varying results of the different studies. The establishment of the gut microbial population is not strictly a succession in the ecological sense; it is rather a complex process influenced by microbial and host interactions and by external and internal factors. The climax intestinal flora is attained in successive stages. The foetal intestine is sterile and bathed in swallowed amniotic fluid. Following delivery, multiple different antigens challenge the intestine of the newborn. The maternal intestinal flora is a source of bacteria for the neonatal gut. The bacterial flora is usually heterogeneous during the first few days of life, independently of feeding habits. After the first week of life, a stable bacterial flora is usually established. In full-term infants a diet of breast milk induces the development of a flora rich in Bifidobacterium spp. Other obligate anaerobes, such as Clostridium spp. and Bacteroides spp., are more rarely isolated and also enterobacteria and enterococci are relatively few. During the corresponding period, formula-fed babies are often colonized by other anaerobes in addition to bifidobacteria and by facultatively anaerobic bacteria; the development of a "bifidus flora" is unusual. In other studies the presence of a consistent number of bifidobacteria in infants delivered in large urban hospitals has not been demonstrated, whether the babies were bottle fed or exclusively breastfed. The predominant faecal bacteria were coliforms and bacteroides. According to these studies, environmental factors may be more important than breastfeeding in gut colonization after delivery. Environmental factors are indeed extremely important for the intestinal colonization of infants born by caesarean section. In these infants, the establishment of a stable flora characterized by a low incidence of Bacteroides spp. and by the isolation of few other bacteria is consistently delayed. In extremely low-birthweight infants, hospitalization in neonatal intensive care units, characterized by prolonged antibiotic therapy, parenteral nutrition, delayed oral feedings and intubation seems to affect the composition of the intestinal microbiota. The gut is colonized by a small number of bacterial species; Lactobacillus and Bifidobacteria spp. are seldom, if ever, identified. According to the few studies so far performed, the predominant species are Enterococcus faecalis, E. coli, Enterobacter cloacae, Klebsiella pneumoniae, Staphylococcus epidermidis and Staphylococcus haemolyticus. Hygienic conditions and antimicrobial procedures strongly influence the intestinal colonization pattern.     

Upper intestinal bacterial flora during transpyloric feeding.

Samples from the pharynx, stomach, duodenum or jejunum, and faeces were collected on 7 days between 1st and 28th day from neonates weighing less than 1.5 kg at birth who were fed by transpyloric tube. These were cultured on selective and non-selective media, and the results were expressed in a semi-quantitative manner. The number of bacterial species and the density of their growth increased with the patient''s age; this was particularly noticeable with Gram-negative bacteria and the ratio of Gram-negative to Gram-positive organisms increased steadily in specimens from all sites with increasing age. The upper small intestine was more heavily colonised than the stomach early in life and the microflora present was predominantly faecal in nature. The species isolated from all sites were mainly aerobes or facultative anaerobes; strict anaerobes did not form a significant proportion of the microflora in these infants. Necrotising enterocolitis developed only after heavy jejunal colonisation with Gram-negative bacilli.     

头孢曲松对乳鼠肠道上皮组织及肠道菌群的影响

目的 探究头孢曲松对生命早期小鼠肠道上皮组织及肠道菌群的影响,以及对成年期小鼠肠上皮组织恢复及菌群再建的影响。方法 36只BALB/C新生小鼠随机分为对照组和实验组（n=18）。实验组小鼠在出生后21 d内,每日用头孢曲松（100 mg/kg）灌胃,对照组用等量生理盐水灌胃。采用免疫组化法检测小鼠肠道各部位上皮细胞相关蛋白（Ki67、Muc2、ZO-1）表达;qPCR和二代测序法分析小鼠粪便细菌总浓度及粪便细菌组成。结果 头孢曲松干预21 d时,与对照组比较,实验组小鼠体重、肠上皮细胞相关蛋白Ki67、ZO-1表达降低,Muc2表达升高（P < 0.05）;总细菌浓度下降但丰富度及多样性增高（P < 0.05）;粪便细菌以厚壁菌门为主,含较多葡萄球菌和肠球菌。生后56 d时,实验组小鼠肠道上皮组织有所恢复,但体重、菌群群落结构等仍和对照组比较差异有统计学意义（P < 0.05）。结论 早期头孢曲松干预能显著损伤机体早期肠道上皮组织的发育和肠道菌群的构建,肠道菌群在生命早期的损伤会部分地延续到成年期,有可能继续影响机体在成年期各种生长发育及生理代谢。     

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目的探讨儿童幽门螺杆菌(H.pylori)感染及抗H.pylori治疗对儿童肠道菌群状态的影响。方法将浙江大学医学院附属儿童医院2004年410月门诊收治的68例慢性胃炎、十二指肠球炎患儿分为H.pylori阳性组36例、H.pylori阴性组32例二组。称取68例患儿新鲜粪便1.0g,分别进行需氧和厌氧培养,分离肠道菌群中最有代表性的三种需氧菌(肠杆菌、肠球菌、酵母菌)和四种厌氧菌(双歧杆菌、乳杆菌、类杆菌、产气荚膜梭菌),菌落记数,同时计算B/E比值来代表定植抗力。对36例H.pylori阳性组中的26例患儿进行“三联”抗H.pylori治疗1周后留取新鲜粪便进行肠道菌群分析,5例患儿在停药1个月后再次进行肠道菌群分析。结果H.pylori阳性组和H.pylori阴性组上述三种需氧菌和四种厌氧菌的菌落检出率比较,差异无统计学意义(P>0.05)。抗H.pylori治疗1周后双歧杆菌、乳杆菌、类杆菌菌落数量较治疗前明显降低(P<0.05),B/E值明显下降(P<0.01),酵母菌的检出率明显增加(P<0.05),产气荚膜梭菌检出率下降(P<0.05)。5例患儿在停药1个月后,乳酸杆菌数量仍继续下降,肠杆菌数量继续增加,双歧杆菌、类杆菌数量有所恢复,但仍低于治疗前。结论儿童H.pylori感染后对肠道菌群影响不大;三联疗法抗H.pylori治疗对儿童肠道菌群产生明显的影响,因此在治疗H.pylori感染时须考虑到大量抗生素治疗后可能对患儿的副作用及潜在的危险。     

Illumina高通量测序技术分析早产儿出生后肠道菌群变化的初步研究

目的 初步探讨NICU早产儿出生后肠道菌群变化特征及其与败血症的关系。方法 以复旦大学附属儿科医院NICU住院的早产儿为研究对象,于出生后第1天采集胎粪,之后于每周龄时或评估败血症时采集粪便样本,直至出院或生后8周。采用Illumina高通量测序技术对粪便样本中所有细菌的16S rRNA-V3区进行DNA测序,应用MG-RAST V3.3.6分析和统计样品序列数目、操作分类单元（OTU）数量,分析肠道菌群物种丰度和分布,并进行聚类分析。结果 3例早产儿共采集生后1、7、14和21 d的12份粪便样本,其中5份样本PCR扩增失败,7份样本(例1生后14、21 d;例2生后7、21 d;例3生后7、14、21 d)DNA测序成功进入分析。3例早产儿平均胎龄为（31.3±0.8）周,平均出生体重为（1 540±144） g。3例均生后应用抗生素,其中例1母亲有产前抗生素暴露史;例2在住院过程中发生全身炎症反应综合征。①7份样本稀疏曲线表明测序深度充分。物种多样性分析显示OTU值为381~608,微生物丰度较高,且与日龄呈正相关,其中例2生后7 d样本肠道菌群多样性最低;②7份样本共检测到18个菌门,均以放线菌门、拟杆菌门、厚壁菌门和变形菌门为优势菌门;变形菌门在例1生后14和21 d样本分别占97.52％和49.11％,放线菌门在例2生后7 d样本占99.46％;③共检测到172个科,其中63科为7份样本共有;相对丰度≥1％的科共检测到10个,例2生后7 d样本棒状杆菌科占97.90％,21 d样本中葡萄球菌科占27.16％;④聚类分析显示,同一研究对象不同时点肠道微生物相似性较高。结论 早产儿产前抗生素暴露及出生后早期抗生素暴露可能会显著降低肠道微生物的多样性,影响正常菌群的定植。发展为败血症的早产儿生后肠道微生物多样性较低,以致病菌占优势的肠道微生物区可能与败血症的发生相关。     

Probiotic intervention in the first months of life: short-term effects on gastrointestinal symptoms and long-term effects on gut microbiota

OBJECTIVES: To determine whether probiotics administered for 6 months postnatally affect gastrointestinal symptoms, crying and the compositional development of the gut microbiota through infancy. METHODS: The study comprised of 132 newborns whose mothers were randomized to receive placebo or Lactobacillus rhamnosus GG (ATCC 53103) before delivery. The treatments of mothers/infants continued for 6 months postnatally. A specific symptom chart was used to monitor gastrointestinal symptoms and infant's crying during the 7th and the 12th weeks of life. Fluorescent in situ hybridization was used to establish the Bifidobacterium, Lactobacillus/Enterococcus, Bacteroides and Clostridium counts in fecal samples at 6, 12, 18 and 24 months of age. RESULTS: Numbers of different types of stools, vomits and crying time were comparable between the groups during the 7th and the 12th weeks of life. Dominant microbiota consisted of bifidobacteria throughout the study. At 6 months, there were less clostridia in faeces in the placebo compared with the probiotic group (P = 0.026), whereas after long-term follow-up at 2 years, there were less lactobacilli/enterococci and clostridia in faeces in the probiotic group than in the placebo group (P = 0.011 and P = 0.032, respectively), reflecting the impact of clostridia as a marker of microbiota succession in healthy infants. CONCLUSIONS: Probiotic administration in the first months of life was well tolerated and did not significantly interfere with long-term composition or quantity of gut microbiota.     

Intestinal colonization leading to fecal urobilinoid excretion may play a role in the pathogenesis of neonatal jaundice

BACKGROUND: Neonatal hyperbilirubinemia remains of concern because of the potential danger for the central nervous system. Because urobilinogen is a nontoxic derivative of bilirubin, the current study was conducted to examine the fecal excretion of urobilinoids and bilirubin in healthy newborns and infants, as well as their intestinal bacteria capable of reducing bilirubin, to assess a possible relation to serum bilirubin levels during the first weeks of life. METHODS: Bilirubin pigments, urobilinoids, and porphyrins were measured in stools of infants during the first week (group A, n = 60) and between the second week and the first 6 months of life (group B, n = 64). Microbiologic analysis of stools was performed in selected cases and bilirubin-converting activity of isolated bacteria was determined in vitro. RESULTS: Urobilinoids were detectable in stools of 57% of the neonates at day 5, but not before. However, fecal urobilinoid production on that day was only a fraction of that observed in adults (0.07 vs. 0.7-3.6 mg/kg per day), whereas at week 6 it increased significantly to an average of 0.9 mg/kg per day. Microbiologic analysis of neonatal stools revealed two novel bacterial strains of Clostridium perfringens and Clostridium difficile capable of reducing bilirubin to urobilinoids. CONCLUSIONS: Urobilinoids can be detected in stools of 57% of newborns at day 5 after delivery. However, the urobilinoid production during the first week of life is quantitatively insufficient to contribute significantly to the removal of bilirubin. Enhancement of the microbial conversion of bilirubin could decrease the intestinal concentration of bilirubin and may decrease the degree or enhance the removal of neonatal hyperbilirubinemia.