Satokari R, Grönroos T, Laitinen K, Salminen S, Isolauri E
Functional Foods Forum, University of Turku, Itäinen Pitkäkatu 4A, Turun Yliopisto, Finland.
Lett Appl Microbiol. 2009 Jan;48(1):8-12. doi: 10.1111/j.1472-765X.2008.02475.x. Epub 2008 Oct 17.
Bifidobacteria and lactobacilli are part of the human normal intestinal microbiota and may possibly be transferred to the placenta. It was hypothesized that intestinal bacteria or their components are present in the placenta and that the foetus may be exposed to them. We investigated the presence of bifidobacteria and lactobacilli and their DNA in the human placenta.
We studied 34 human placentae (25 vaginal and nine caesarean deliveries) for the presence Bifidobacterium spp. and Lactobacillus rhamnosus. Cultivation was used for the detection of viable cells and genus and species-specific PCR for the detection of DNA. No bifidobacteria or lactobacilli were found by cultivation. Bifidobacterial DNA was detected in 33 and L. rhamnosus DNA in 31 placenta samples.
DNA from intestinal bacteria was found in most placenta samples. The results suggest that horizontal transfer of bacterial DNA from mother to foetus may occur via placenta.
Bacterial DNA contains unmethylated CpG oligodeoxynucleotide motifs which induce immune effects. Specific CpG motifs activate Toll-like receptor 9 and subsequently trigger Th-1-type immune responses. Although the newborn infant is considered immunologically immature, exposure by bacterial DNA may programme the infant's immune development during foetal life earlier than previously considered.
双歧杆菌和乳酸杆菌是人类正常肠道微生物群的一部分，可能会转移至胎盘。据推测，肠道细菌或其成分存在于胎盘中，胎儿可能会接触到它们。我们调查了双歧杆菌和乳酸杆菌及其DNA在人胎盘中的存在情况。
我们研究了34份人胎盘（25例经阴道分娩和9例剖宫产）中双歧杆菌属和鼠李糖乳杆菌的存在情况。采用培养法检测活细胞，用属和种特异性PCR检测DNA。培养法未发现双歧杆菌或乳酸杆菌。在33份胎盘样本中检测到双歧杆菌DNA，在31份胎盘样本中检测到鼠李糖乳杆菌DNA。
大多数胎盘样本中发现了肠道细菌的DNA。结果表明，细菌DNA可能通过胎盘从母亲水平转移至胎儿。
细菌DNA含有可诱导免疫效应的未甲基化CpG寡脱氧核苷酸基序。特定的CpG基序可激活Toll样受体9，随后引发Th-1型免疫反应。尽管新生儿被认为免疫不成熟，但细菌DNA的暴露可能比之前认为的更早地在胎儿期对婴儿的免疫发育进行编程。
