Biology:Placental microbiome
The placental microbiome is the nonpathogenic, commensal bacteria claimed to be present in a healthy human placenta and is distinct from bacteria that cause infection and preterm birth in chorioamnionitis.[1] Until recently, the healthy placenta was considered to be a sterile organ but now genera and species have been identified that reside in the basal layer.[2][1]
It should be stressed that the evidence for a placental microbiome is controversial.[3][4] Most studies supporting the existence of a placental microbiome lack the appropriate experimental controls, and it has been found that contamination is most likely responsible for reports of a placental microbiome.[3][5]
The placental microbiome more closely resembles that of the oral microbiome than either the vaginal or rectal microbiome.[1]
Bacterial species and genera
Culturable and non-culturable bacterial species in the placenta obtained following normal term pregnancy have been identified.
| Binomial name | Commensal | Transient | Potential pathogen |
References |
|---|---|---|---|---|
| Prevotella tannerae | x | x | [6][7][8] | |
| Bacillota spp | x | x | [9][10] | |
| Mycoplasmatota ssp. | x | x | [9] | |
| Fusobacterium nucleatum | x | x | [11][12] | |
| Prevotella tanerae | x | |||
| Bacteroides spp. | x | x | [10] | |
| Fusobacterium spp. | x | x | ||
| Streptomyces avermitilis | x | [10] | ||
| Neisseria polysaccharea | x | |||
| Neisseria lactamica | x | |||
| Pseudomonadota ssp. | x | [9][10] | ||
| Bacteroidota ssp. | x | [9] | ||
| Escherichia coli | x | x | [8] | |
| Escherichia ssp. | x | x | [8] | |
| Actinomycetota ssp. | x | x | [10] | |
| "Cyanobacteria" ssp. | x | [10] | ||
| Chloroflexota ssp. | x | [10] | ||
| Aquificota ssp. | x | [10] | ||
| Verrucomicrobiota ssp. | x | [10] | ||
| Vibrio ssp. | x | [10] | ||
| Burkholderia ssp. | x | [10] | ||
| Beijerinckia ssp. | x | [10] |
In a healthy placental microbiome, the diversity of the species and genera is extensive.[1] A change in the composition of the microbiota in the placenta is associated with excess gestational weight gain, and pre-term birth.[10] The placental microbiota varies between low birth weight infants and those infants with normal birth weights.[13] While bacteria are often found in the amniotic fluid of failed pregnancies, they are also found in particulate matter that is found in about 1% of healthy pregnancies.[9]
In non-human animals, part of the microbiome is passed onto offspring even before the offspring are born. Bacteriologists assume that the same probably holds true for humans.[9]
Research
The fact that germ free animals can be routinely generated by sterile cesarean section provides strong experimental evidence for the sterile womb hypothesis.
Future research may find that the microbiota of the female reproductive tract may be related to pregnancy, conception, and birth. Animal studies have been used to investigate the relationship between oral microbiota and the placental microbiota. Mice inoculated with species of oral bacteria demonstrated placental colonization soon afterwards.[14]
History
Investigations into reproductive-associated microbiomes began around 1885 by Theodor Escherich. He wrote that meconium from the newborn was free of bacteria. This was interpreted as the uterine environment being sterile. Other investigations used sterile diapers for meconium collection. No bacteria were able to be cultured from the samples. Bacteria were detected and were directly proportional to the time between birth and the passage of meconium. A 1927 study demonstrated the presence of bacteria in the amniotic fluid of those that were in labor for longer than six hours.[15]
See also
- Human microbiome
- Human microbiome project
- Human virome
- List of bacterial vaginosis microbiota
- Microbiota of the lower reproductive tract of women
- Vaginal microbiota in pregnancy
References
- ↑ 1.0 1.1 1.2 1.3 "Maternal microbiome and pregnancy outcomes". Fertility and Sterility 104 (6): 1358–63. 2015. doi:10.1016/j.fertnstert.2015.09.037. PMID 26493119.
- ↑ Schwiertz, Andreas; Rusch, Volker (2016). "A Short Definition of Terms". in Schwiertz, Andreas. Microbiota of the Human Body. Advances in Experimental Medicine and Biology. pp. 1–3. ISBN 978-3-319-31248-4.
- ↑ 3.0 3.1 Perez-Muñoz, Maria Elisa; Arrieta, Marie-Claire; Ramer-Tait, Amanda E.; Walter, Jens (2017-04-28). "A critical assessment of the "sterile womb" and "in utero colonization" hypotheses: implications for research on the pioneer infant microbiome". Microbiome 5 (1): 48. doi:10.1186/s40168-017-0268-4. ISSN 2049-2618. PMID 28454555.
- ↑ Kliman, Harvey J. (2014-09-17). "Comment on "The placenta harbors a unique microbiome"" (in en). Science Translational Medicine 6 (254): 254le4. doi:10.1126/scitranslmed.3009864. ISSN 1946-6234. PMID 25232175.
- ↑ Lauder, Abigail P.; Roche, Aoife M.; Sherrill-Mix, Scott; Bailey, Aubrey; Laughlin, Alice L.; Bittinger, Kyle; Leite, Rita; Elovitz, Michal A. et al. (2016-06-23). "Comparison of placenta samples with contamination controls does not provide evidence for a distinct placenta microbiota". Microbiome 4 (1): 29. doi:10.1186/s40168-016-0172-3. ISSN 2049-2618. PMID 27338728.
- ↑ "Antimicrobial peptides in the female reproductive tract: a critical component of the mucosal immune barrier with physiological and clinical implications". Human Reproduction Update 21 (3): 353–77. 2015. doi:10.1093/humupd/dmu065. PMID 25547201.
- ↑ "Trophoblast-microbiome interaction: a new paradigm on immune regulation". American Journal of Obstetrics and Gynecology 213 (4 Suppl): S131–7. 2015. doi:10.1016/j.ajog.2015.06.039. PMID 26428492.
- ↑ 8.0 8.1 8.2 Todar, K.. "Pathogenic E. coli". Online Textbook of Bacteriology. University of Wisconsin–Madison Department of Bacteriology. http://www.textbookofbacteriology.net/e.coli.html.
- ↑ 9.0 9.1 9.2 9.3 9.4 9.5 "Is a foetus developing in a sterile environment?". Letters in Applied Microbiology 59 (6): 572–9. 2014. doi:10.1111/lam.12334. PMID 25273890.
- ↑ 10.00 10.01 10.02 10.03 10.04 10.05 10.06 10.07 10.08 10.09 10.10 10.11 10.12 "The preterm placental microbiome varies in association with excess maternal gestational weight gain". American Journal of Obstetrics and Gynecology 212 (5): 653.e1–16. 2015. doi:10.1016/j.ajog.2014.12.041. PMID 25557210.
- ↑ "The microbiome, parturition, and timing of birth: more questions than answers". Journal of Reproductive Immunology 104–105: 12–9. 2014. doi:10.1016/j.jri.2014.03.006. PMID 24793619.
- ↑ "Vaginal indicators of amniotic fluid infection in preterm labor". Obstetrics and Gynecology 97 (2): 211–9. 2001. doi:10.1016/s0029-7844(00)01146-7. PMID 11165584.
- ↑ "The Placental Microbiome Varies in Association with Low Birth Weight in Full-Term Neonates". Nutrients 7 (8): 6924–37. 2015. doi:10.3390/nu7085315. PMID 26287241.
- ↑ The Human Microbiota : How Microbial Communities Affect Health and Disease. Fredricks, David N.. Hoboken, New Jersey: Wiley-Blackwell. 2013. pp. 156, 169. ISBN 9780470479896. OCLC 794922809.
- ↑ "A critical assessment of the "sterile womb" and "in utero colonization" hypotheses: implications for research on the pioneer infant microbiome". Microbiome 5 (1): 48. 2017. doi:10.1186/s40168-017-0268-4. PMID 28454555.
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