Husso Aleksi, Lietaer Leen, Pessa-Morikawa Tiina, Grönthal Thomas, Govaere Jan, Van Soom Ann, Iivanainen Antti, Opsomer Geert, Niku Mikael
Department of Veterinary Biosciences, Faculty of Veterinary Medicine, University of Helsinki, Helsinki, Finland.
Department of Reproduction, Obstetrics and Herd Health, Faculty of Veterinary Medicine, Ghent University, Merelbeke, Belgium.
Front Microbiol. 2021 Apr 30;12:626421. doi: 10.3389/fmicb.2021.626421. eCollection 2021.
The development of a healthy intestinal immune system requires early microbial exposure. However, it remains unclear whether microbial exposure already begins at the prenatal stage. Analysis of such low microbial biomass environments are challenging due to contamination issues. The aims of the current study were to assess the bacterial load and characterize the bacterial composition of the amniotic fluid and meconium of full-term calves, leading to a better knowledge of prenatal bacterial seeding of the fetal intestine. Amniotic fluid and rectal meconium samples were collected during and immediately after elective cesarean section, performed in 25 Belgian Blue cow-calf couples. The samples were analyzed by qPCR, bacterial culture using GAM agar and 16S rRNA gene amplicon sequencing. To minimize the effects of contaminants, we included multiple technical controls and stringently filtered the 16S rRNA gene sequencing data to exclude putative contaminant sequences. The meconium samples contained a significantly higher amount of bacterial DNA than the negative controls and 5 of 24 samples contained culturable bacteria. In the amniotic fluid, the amount of bacterial DNA was not significantly different from the negative controls and all samples were culture negative. Bacterial sequences were identified in both sample types and were primarily of phyla Proteobacteria, Firmicutes, Bacteroidetes, and Actinobacteria, with some individual variation. We conclude that most calves encounter maternal-fetal transmission of bacterial DNA, but the amount of bacterial DNA is low and viable bacteria are rare.
健康肠道免疫系统的发育需要早期接触微生物。然而，微生物接触是否在产前阶段就已开始仍不清楚。由于污染问题，分析这种低微生物生物量环境具有挑战性。本研究的目的是评估足月小牛羊水和胎粪中的细菌载量并表征其细菌组成，从而更好地了解胎儿肠道的产前细菌定植情况。在25对比利时蓝牛犊夫妇进行选择性剖宫产期间及术后立即采集羊水和直肠胎粪样本。通过qPCR、使用GAM琼脂的细菌培养以及16S rRNA基因扩增子测序对样本进行分析。为了尽量减少污染物的影响，我们纳入了多个技术对照，并严格过滤16S rRNA基因测序数据以排除假定的污染序列。胎粪样本中的细菌DNA含量明显高于阴性对照，24个样本中有5个含有可培养细菌。在羊水中，细菌DNA含量与阴性对照无显著差异，所有样本培养均为阴性。在两种样本类型中均鉴定出细菌序列，主要为变形菌门、厚壁菌门、拟杆菌门和放线菌门，存在一些个体差异。我们得出结论，大多数小牛会经历母胎细菌DNA传播，但细菌DNA含量较低且活细菌很少。
