最近的研究对无菌子宫的概念提出了挑战,这些研究描述了包括人类和牛在内的原始子宫和怀孕子宫的微生物组。我们设计了两项研究,测试了处女母牛首次授精时微生物组是否被引入子宫,以及微生物组的起源是否是阴道/子宫颈。
■在人工授精之前和之后立即测量子宫微生物组(AI;研究1;n=7AI和n=6对照)和授精后14d(研究2;n=12AI和n=12对照)在AI和非AI(对照)荷斯坦母牛中。随后进行包括额外阴性对照的第三项研究(研究3;n=5只荷斯坦母牛),以支持子宫内独特微生物组的存在,尽管微生物生物量低并且不考虑授精。除了对相同样品进行16SrRNA基因测序之外,还进行传统的细菌学培养,以确定除了基于DNA测序(16SrRNA基因序列)检测到的生物之外,是否存在活生物体。
■通过传统的细菌培养或代谢(16SrRNA基因)测序方法进行评估时,对小母牛进行人工授精不会导致微生物组的大的变化(研究1和2的结果)。无论是否进行AI(阴性对照),从子宫的身体或角中培养的细菌很少。培养的细菌属(例如,芽孢杆菌,棒状杆菌,Cutubacterium,微球菌,葡萄球菌,和链球菌)是典型的在土壤中发现的,环境,皮肤,粘膜,和动物的泌尿生殖道。16SrRNA基因的代谢测序产生了大量的扩增子序列变异体(ASV),但是这些基于DNA测序的较大数据集并没有一致地证明AI对所有子宫位置的ASV丰度的影响与管道的外表面相比(例如,perimetrium;屠宰和收集过程中环境污染的阳性对照样品)。16SrRNA基因测序鉴定出的主要属与细菌培养鉴定出的属重叠,包括镰状杆菌,葡萄球菌,和链球菌。
UNASSIGNED: The concept of a sterile uterus was challenged by recent studies that have described the microbiome of the virgin and pregnant uterus for species including humans and cattle. We designed two studies that tested whether the microbiome is introduced into the uterus when the virgin heifer is first inseminated and whether the origin of the microbiome is the vagina/cervix.
UNASSIGNED: The uterine microbiome was measured immediately before and after an artificial insemination (AI; Study 1; n = 7 AI and n = 6 control) and 14 d after insemination (Study 2; n = 12 AI and n = 12 control) in AI and non-AI (control) Holstein heifers. A third study (Study 3; n = 5 Holstein heifers) that included additional negative controls was subsequently conducted to support the presence of a unique microbiome within the uterus despite the low microbial biomass and regardless of insemination. Traditional bacteriological culture was performed in addition to 16S rRNA gene sequencing on the same samples to determine whether there were viable organisms in addition to those detected based on DNA sequencing (16S rRNA gene sequence).
UNASSIGNED: Inseminating a heifer did not lead to a large change in the microbiome when assessed by traditional methods of bacterial culture or metataxonomic (16S rRNA gene) sequencing (results of Studies 1 and 2). Very few bacteria were cultured from the body or horn of the uterus regardless of whether an AI was or was not (negative control) performed. The cultured bacterial genera (e.g., Bacillus, Corynebacterium, Cutibacterium, Micrococcus, Staphylococcus, and Streptococcus) were typical of those found in the soil, environment, skin, mucous membranes, and urogenital tract of animals. Metataxonomic sequencing of 16S rRNA gene generated a large number of amplicon sequence variants (ASV), but these larger datasets that were based on DNA sequencing did not consistently demonstrate an effect of AI on the abundance of ASVs across all uterine locations compared with the external surface of the tract (e.g., perimetrium; positive control samples for environment contamination during slaughter and collection). Major genera identified by 16S rRNA gene sequencing overlapped with those identified with bacterial culture and included Cutibacterium, Staphylococcus, and Streptococcus.