Researchers from the University of Toronto partnered with The Hospital For Sick Children and found that mothers of preterm babies have unique breast milk microbiomes, and that even short courses of antibiotics can leave lasting effects on the diversity and microbe abundance in their milk.
It’s no secret that breastmilk is elusive in many of its beneficial properties, but as we learn more about it, we learn how tremendously unique it is to mothers and babies.
Not only does breastmilk have unique microbiomes, but researchers from the University of Toronto and The Hospital for Sick Children also found that even short courses of antibiotics can have prolonged effects on the abundance of and diversity in microbes in the milk of mothers to preterm babies.
The study, the largest to date of breast milk microbiota in moms of preterm babies, is the first to show that antibiotic exposure have effects on the most common microbes in breast milk. The class, timing and duration of exposure in a mother can potentially influence growth and immunity to disease in newborns, and particularly in preterm babies susceptible to complications.
Deborah O’Connor is a professor and chair of nutritional sciences at the University of Toronto and a senior associate scientist at SickKids. She said that the team was shocked to see that even one day of antibiotics was associated with significant changes in the microbiota of breast milk. O’Connor says that the big take-away is that though antibiotics may be an essential treatment for mothers of preterm babies, the use should be carefully assessed for risk by clinicians subscribing and patients taking them.
O’Connor was the principal investigator of the study and said that most antibiotic stewardship programs in NICUs focus on limited use of antibiotics in newborns, but that the current study suggests that clinicians should consider limited use in mothers as well.
The study included 490 breast milk samples from 86 moms of preterm babies. The milk was collected during the first eight weeks of their deliveries. Body Mass Index and delivery mode greatly influenced breast milk microbiota, as is consistent with other studies that have found the same.
But, in these mothers of preterm babies, the effects of antibiotics uses was most pronounced, and in some cases, that lasted for weeks. Many antibiotic-induced changes were ones that affected key microbes that are known to play a role in fostering disease or on metabolic processes that promote babies’ development and growth or their gut health.
Michelle Asbury is a doctoral student in O’Connor’s lab and a lead author of the study. She said that particular concern was the association between antibiotics and a member of the of the Proteobacteria phylum called Pseudomonas. When elevated in a preterm baby’s gut, Proteobacteria can precede necrotizing enterocolitis, a life-threatening condition.
Close to seven percent of preterm babies develop necrotizing enterocolitis. It’s sadly not uncommon for the condition, in which part of the bowel dies, to be fatal.
The team also found that the cephalosporin class of antibiotics also had a big effect on diversity of breast milk microbiota.
The team says it’s still too early to tell what the findings mean for preterm infant health and longterm outcomes. They’re comparing their findings with stool samples from the babies of the mothers involved in the study. This would show whether the changes in their mothers’ milk microbiomes seed the babies’ guts to promote health or increase their risk of disease.
Still, the study did show enough association to pay attention to the use of antibiotics–particularly if there’s mastitis, blood infections or membranes rupturing early. But, over 60% of the women in the study had some course of antibiotic, and researchers also were worried about the potential for overuse in treatment protocols.
Sharon Unger is a professor of pediatrics at the University of Toronto and a scientist and neonatologist at Sinai Health and SickKids. She also co-authored the study. Unger said that breastfeeding benefits far outweigh risk that antibiotics may pose in disrupting breast milk microbiomes, and of course, mothers should continue to give their own milk whenever possible.
But she also believes that it’s important to narrow the spectrum of antibiotics used and look at shortening duration of use if possible to disrupt less.