Katariina Pärnänen on Breastfeeding and Bacteria Resistance in Infants
Nearly 214,000 annual neonatal deaths are attributed to septic infections caused by antibiotic resistant pathogens, which epitomizes an antibiotic resistance crisis among infants.
An infant’s gut contains a high abundance of antibiotic-resistance genes (ARGs) compared with adults, even when infants have not been exposed to antibiotics. Breast milk—the primary source of food for infants during their first months—shapes the infant’s gut microbiota, yet its impact on the resistome was undetermined.
Katariina Pärnänen, microbiologist and PhD student in the department of microbiology at University of Helsinki in Finland, is the lead author of a new study1 about the topic and answered our questions about the outcomes of her research.
Gastroenterology Consultant: How did your study come about?
Katariina Pärnänen: We were interested to see why infants have more genes that confer resistance to antibiotics in their gut bacteria than adults. ARGs can make bacteria that carry them in their genomes resistant to antibiotics, which means that infections caused by bacteria carrying ARGs cannot be treated with antibiotics. This is a problem in infants, who generally have a weaker immune system than adults and who have more infections that need to be treated with antibiotics than adults. Annually, an estimated 200,000 infants die from infections caused by resistant bacteria that spread to the blood stream.
In light of the graveness of the issue, we wanted to know where the ARGs are coming from. We investigated whether the genes come from the baby’s mother—either from breast milk or the gut—and also how antibiotic treatment of mothers during delivery and breastfeeding affect the abundance of antibiotic-resistant bacteria in the gastrointestinal tract of infants.
GASTRO CON: Why is antibiotic resistance considered a global health threat?
KP: Before the discovery and efficient manufacturing of antibiotics, the leading cause for death was infection. Infections caused by bacteria could not be efficiently treated and many routine medical procedures, such as small surgeries, were extremely risky due to the likely chance of infection. Bacteria can evolve very rapidly compared with many other organisms. So, when humans started to use antibiotics, bacteria were able to rapidly evolve resistance against antibiotics. Every time a new antibiotic has come to the market, clinical strains with resistance against the new antibiotic emerge usually in less than 3 years.
Bacteria have very flexible genomes compared with mammals, and they can have tens of genes only encoding antibiotic resistance for different kinds of antibiotics. This is why we see so-called ‘superbugs,’ which are resistant to all available antibiotics. These ‘superbugs’ are becoming more and more abundant, and there is a risk that mortality rates of infections will go back to the same levels as in the preantibiotic era, when infections were the number one killer. The World Health Organization (WHO) has estimated that, in 2050, approximately 10 million people will die due to antimicrobial resistance, which is more than the number for cancer.
Antibiotic resistance in bacteria is becoming more common as more antibiotics are used. It does not matter whether the antibiotic is used correctly or incorrectly to treat viral infections. Antibiotic use is also very common in meat production, and people can acquire antibiotic-resistant bacteria from food.
Also, neonates have antibiotic-resistant bacteria in their gut, even when they have never been exposed to antibiotics. Recent studies show that infants have many more resistance genes in their gut bacteria than adults, which is alarming.
GASTRO CON: What is the most important correlation you observed in your study?
KP: We saw that infants who were partially or exclusively breastfed for 6 months or longer had fewer elevated ARGs compared with infants who were not breastfed at all or who were breastfed for a shorter time. This tells us that breastfeeding can reduce the abundance of antibiotic-resistant bacteria in the infant’s gut in addition to the many other health benefits it has for the infant.
GASTRO CON: What do the results convey about early termination of breastfeeding? Can it lead to antibiotic resistance?
KP: Terminating breastfeeding early has been shown to decrease the abundance of beneficial bacteria, such as bifidobacteria—which are used in common probiotics— in the infant’s gut. This is because the sugars in breast milk are good food for bifidobacteria and help them gain ground from other bacteria. When breastfeeding is terminated early and formula is given to babies instead, other bacteria can dominate the gut. When the infant is given formula, the bacteria that grow well in the infant’s gut are unfortunately also ones that can cause infections and have been very efficient in collecting ARGs in their genomes. These bacteria belong to the family Enterobacteriaceae and include many strains that are opportunistic pathogens, which means that they can cause infection under the right circumstances. The effect of formula is seen very drastically in preterm infants who often suffer from a serious infectious disease called necrotising enterocolitis (NEC), for which the biggest risk factor, besides prematurity, is formula. This is why preterm infants usually are given donor breast milk instead of formula if the mother’s breast milk needs to be supplemented.
So, in short, terminating breastfeeding early can lead to the increased abundance of antibiotic-resistant bacteria, which also often cause disease.
GASTRO CON: What do you recommend as the ideal duration of breastfeeding?
KP: Based on our study, I would recommend that breastfeeding is continued until 6 months of age at the very minimum. At 6 months, infants start to consume solid food, so the impact of terminating breastfeeding after this might not have as drastic effects. Even though the recommended duration of breastfeeding is 2 years according to WHO, very few mothers breastfeed even until the baby is 6 months.
However, breastmilk is good food for beneficial bacteria and benefits infant health in many ways. Health care professionals should educate their patients who have recently become mothers on the facts of breastfeeding longer, and so their patients will feel comfortable asking for help relating to breastfeeding.
Breastfeeding education is still lacking in many countries, and I think that adherence to breastfeeding could be increased by improving education and increasing the amount of support that mothers have for continuing to breastfeed when there are problems.
Reference:
1) Pärnänen K, Karkman A, Hultman J, et al. Maternal gut and breast milk microbiota affect infant gut antibiotic resistome and mobile genetic elements. Nat Commun. 2018;9(1):3891. https://www.nature.com/articles/s41467-018-06393-w.