Nav: Home

Researchers devise methods to identify transmission of microbes from mothers to infants

January 17, 2017

WASHINGTON, DC - January 17, 2017 - It has been assumed that mothers pass on gut microbes to their infants during and just after delivery, a process called vertical transmission, but because of limits in available technology, the evidence of this occurrence has been limited. Now, researchers in Italy have combined laboratory and novel computational techniques to systematically track the vertical transmission of microbes in a pilot study.

Their results, published this week in mSystems, an open access journal from the American Society for Microbiology, found several identical bacterial strains in the microbial communities (the microbiomes) of both infants and their mothers that were distinct from those found in other infants or mothers, a sign of vertical transmission. In addition, transmitted strains from the Bacteroides and Bifidobacterium species were found to be active in both the mother and infant gut microbial communities.

"Early infant exposure is important in the acquisition and ultimate development of a healthy microbiome," said senior study author Nicola Segata, PhD, an assistant professor at the Centre for Integrative Biology at the University of Trento, Italy. "We developed methods to identify the vertical flow of microorganisms from mothers to infants and showed that mothers are sources of microbes that might be important in the development of the infant gut microbiome."

Previous cultivation-free studies have observed the same microbial species within mothers and infants and therefore assumed that transmission occurred "but in reality, unless you can see the same strain or genetic variant, it's very hard to conclude that," said study co-senior author Adrian Tett, PhD, a senior research associate with the Centre. Although some microorganisms have been followed from mothers to infants using time-consuming cultivation approaches, "We demonstrated that vertical transmission can be inferred without using cultivation and will follow up on a larger scale."

There has been debate among scientists whether microbes colonize in the infant gut at birth or in the womb, Segata said. If strong evidence is found that the mother before or during childbirth is likely to transmit a particular microbe that can be detrimental to the infant's future health, he said, it could be possible to test the mother while she is pregnant and offer some preventative treatment. For example, current practice tests pregnant women for Group B Streptococcus that can cause infection in the infant; if the woman tests positive, drugs are administered just before delivery to prevent transmission of the microbe to the infant.

Segata and colleagues collected fecal and breast milk samples from five mother-infant pairs recruited by a local hospital when the infants were three months old. They collected additional samples from two of the mother-infant pairs again when the infants were 10 months old, and from another mother-infant pair when the baby was 16 months old. They applied a laboratory technique called shotgun metagenomic sequencing to 24 microbiome samples (eight mother fecal samples, eight infant fecal samples and eight breast milk samples) to see which microbes were present. They used an additional tool called metatranscriptomics in fecal samples from two of the pairs to see which microbes were active.

Initially, as expected, the mothers' intestines had greater microbial diversity than those of the infants. However, the gut microbiome of the 16-month-old child had shifted toward a more mother-like composition with an increase in microbial diversity. Breast milk samples had limited diversity shortly after birth; skin microbes were observed in only low numbers in the infants' gut microbiomes, suggesting that skin microbes do not colonize the human gut.

To analyze microbial transmission from mother to infant, the team further analyzed the metagenomic samples at a finer level to assess specific bacterial strains using newly developed computational approaches. One infant harbored a strain of the common infant bacterium Bifidobacterium bifidum that was 99.96% identical to his mother's but clearly distinct from B. bifidum strains seen in the other infants and mothers, offering strong evidence for vertical microbial transmission. Another infant had strains of two other bacteria, Coprococcus comes and Ruminococcus bromii, that were over 99% identical to his mother's. From metatranscriptomics, researchers observed some of the same strains of bacteria active in both the mothers' and the infants' guts.

While the results are still early, Segata said, "there is probably a substantial fraction of bacteria in the infant that come from the mothers." In ongoing work, the investigators are studying more mother-infant pairs from the time of the babies' births to over one year of age, including analyses of the mothers' and infants' microbiomes from several body locations. They will compare microbe transmission routes during vaginal and Cesarean section deliveries, breastfeeding, and skin-to-skin contact shortly after birth.
-end-
The study was funded by Fondazione CARITRO, a local foundation, and supported by the Italian Ministry of Education, Universities and Research and by the European Commission.

The American Society for Microbiology is the largest single life science society, composed of over 48,000 scientists and health professionals. ASM's mission is to promote and advance the microbial sciences.

ASM advances the microbial sciences through conferences, publications, certifications and educational opportunities. It enhances laboratory capacity around the globe through training and resources. It provides a network for scientists in academia, industry and clinical settings. Additionally, ASM promotes a deeper understanding of the microbial sciences to diverse audiences.

American Society for Microbiology

Related Microbes Articles:

Microbes seen controlling action of host's genes
Duke researchers have shown that microbes can control their animal hosts by manipulating the molecular machinery of their cells, triggering patterns of gene expression that consequently contribute to health and disease.
Three-way dance between herbivores, plants and microbes unveiled
What looks like a caterpillar chewing on a leaf or a beetle consuming fruit is likely a three-way battle that benefits most, if not all of the players involved, according to a Penn State entomologist.
Vitamin B12: Power broker to the microbes
In the microbial world, vitamin B12 is a hot commodity.
Gut microbes and bird's breath from the U at #SICB2017
University of Utah researchers will be among the scientists convening in New Orleans for the 2017 Annual Meeting for the Society for Integrative and Comparative Biology Jan.
Gut microbes contribute to recurrent 'yo-yo' obesity
New research in mice may in the future help dieters keep the weight off.
Digital microbes for munching yourself healthy
A research team at the Luxembourg Centre for Systems Biomedicine (LCSB) of the University of Luxembourg has taken an important step in modelling the complexity of the human gut's bacterial communities -- the microbiome -- on the computer.
How gut microbes help chemotherapy drugs
Two bacterial species that inhabit the human gut activate immune cells to boost the effectiveness of a commonly prescribed anticancer drug, researchers report Oct.
Soil microbes flourish with reduced tillage
Microbes improve soil quality by cycling nutrients and breaking plant residues down into soil organic matter.
Microbes help plants survive in severe drought
Plants can better tolerate drought and other stressors with the help of natural microbes, University of Washington research has found.
Mix and match microbes to make probiotics last
Scientists have tried to alter the human gut microbiota to improve health by introducing beneficial probiotic bacteria.

Related Microbes Reading:

Best Science Podcasts 2019

We have hand picked the best science podcasts for 2019. Sit back and enjoy new science podcasts updated daily from your favorite science news services and scientists.
Now Playing: TED Radio Hour

Climate Crisis
There's no greater threat to humanity than climate change. What can we do to stop the worst consequences? This hour, TED speakers explore how we can save our planet and whether we can do it in time. Guests include climate activist Greta Thunberg, chemical engineer Jennifer Wilcox, research scientist Sean Davis, food innovator Bruce Friedrich, and psychologist Per Espen Stoknes.
Now Playing: Science for the People

#527 Honey I CRISPR'd the Kids
This week we're coming to you from Awesome Con in Washington, D.C. There, host Bethany Brookshire led a panel of three amazing guests to talk about the promise and perils of CRISPR, and what happens now that CRISPR babies have (maybe?) been born. Featuring science writer Tina Saey, molecular biologist Anne Simon, and bioethicist Alan Regenberg. A Nobel Prize winner argues banning CRISPR babies won’t work Geneticists push for a 5-year global ban on gene-edited babies A CRISPR spin-off causes unintended typos in DNA News of the first gene-edited babies ignited a firestorm The researcher who created CRISPR twins defends...