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Mothers’ antibiotics give newborns irritable bowel disease

Pregnant mothers who take antibiotics put their children at greater risk of inflammatory bowel disease, a new study warned.

The pills, taken by about 40 percent of pregnant women in the US, cause changes in the gut bacteria or microbiome of the mother which are then inherited by their unborn child, according to the New York University study.

The balance between good and bad bacteria is altered and this change triggered a IBD inflammation scores 55-fold higher than those with normal gut bacteria.

Crohn’s disease and ulcerative colitis are the two main forms of IBD, affecting about 1.6 million Americans, including a growing number of children. 

Taking antibiotics while pregnant may weaken the gut microbiomes mothers pass to their babies, leaving the newborns more vulnerable to developing irritable bowel disease 

The microbiome is made up of trillions of bacterial organisms that live inside of our intestines and co-evolved with us to play roles in digestion, metabolism, and immunity.

But as the number children prescribed antibiotics has increased in the past decades, so has incidences of autoimmune conditions like inflammatory bowel disease or IBD.

Earlier this year, a Canadian study generated concern when it found a significant increase in the number of children under five diagnosed with IBD in 2010 over 1999.

While many studies have linked these trends, only a few experiments in mice have shown microbial differences to directly increase disease risk.

It has been suggested antibiotic use changes the mix of maternal microbes transferred to offspring. 

In healthy pregnancies, some of the mother’s microbiome is transferred to the newborn, ‘teaching’ the baby’s own gut bacteria how to to execute normal metabolic and immune functions.

But when antibiotics change the mother’s ‘teaching’ bacteria, the baby’s microbiome will be more likely to to struggle to process what he or she ingests. 

The new study deliberately altered the microbiome with antibiotics before transplanting them in pregnant mice. 

Dr Martin Blaser at New York University (NYU) School of Medicine explained: ‘Our results provide strong evidence that antibiotics change the baby’s inherited microbial communities with long-term disease consequences, which is especially important given the widespread use of antibiotics in young women before and during pregnancy.

‘Our study shows that the changes made to the microbiome by antibiotic exposure can be transmitted across generations, from moms to their offspring, which is consistent with our work and that of others in humans.’

The study, published in the journal Nature Microbiology, involved inoculating pregnant mice with microbiota changed by exposure to antibiotics.

This antibiotic-induced changes in microbial populations persisted in the mothers, who then passed on the differences to their offspring.

Slides from the study show the bowel inflammation of mice that inherited antibiotic-altered gut microbiomes from their mothers (bottom) as compared to healthy mouse pups (top)

Slides from the study show the bowel inflammation of mice that inherited antibiotic-altered gut microbiomes from their mothers (bottom) as compared to healthy mouse pups (top)

The pups had less diverse mix of bacteria with changes in the number of key species and more fluctuations in bacterial species compared to those pups that inherited normal microbiota.

The study then compared pups born from normal mothers with those born from mothers who were engineered to lack the gene for the immune protein interleukin 10 (IL-10).

The protein is known to help to prevent the immune system from creating excess inflammation, so being born without the gene elevates the risk for IBD.  

In the group of IL-10-deficient pups, those that inherited the antibiotic-altered microbiomes from their mothers had IBD inflammation scores 55-fold higher than the pups that inherited a normal microbial population.

Strep B and antibiotics during delivery

For one group of women, antibiotics may be required to deliver a healthy baby. 

Nearly 25 percent of healthy women have streptococcus B bacteria living in their vaginas or rectums.

About one in every 2,000 babies born in contracts the infection at birth. 

If the bacteria is passed to their baby during birth, it can lead to meningitis, pneumonia, heart, breathing and gastrointestinal problems. 

In the US, women are tested for the bacteria between 35 and 37 weeks of pregnancy. 

The bacteria can go away and come back, so taking antibiotics during pregnancy is not helpful. 

If a woman tests positive, she will most likely be given antibiotics during delivery.  

This showed how environmental and genetic factors combine to determine each animal’s risk and confirmed the effects of antibiotic treatment had been passed to the next generation.

Genomic and statistical techniques were then used to analyze the millions of pieces of bacterial DNA in the samples.

Past studies had already matched key DNA sequences to known bacterial species, enabling the team to define each pup’s microbiome, and to watch the effect of each.

The pups’ antibiotic-altered microbe mix included less of the bacterial taxa Erysipelotrichi and more of the Verrucomicrobiae, with more expression of genes that might be particularly damaging to host tissues.

The pathway identified had been previously seen in both mouse and human studies, confirming the relevance of this model.

It is well known that a portion of IBD risk is inherited, but the increased risk due to particular human genes is relatively small.

The study provided evidence that it is instead changes in microbial genes that are the passed from mothers to their children which affects risk.

‘The basis for inheritance of IBD might possibly be quite different from what we had been thinking for many years,’ Dr Blaser concluded. 


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