The researchers at the University of Helsinki found that infants who were breastfed for at least six months had a smaller number of resistant bacteria in their gut. The findings have been published in the journal Nature Communications.
The study demonstrated for the first time that breast milk indeed contains a significant number of genes that provide antibiotic resistance for bacteria, and that these genes, as well as their host bacteria, are most likely transmitted to infants in the milk.
Mothers transmit antibiotic-resistant bacteria residing in their own gut to their progeny in other ways as well, for example through direct contact. Yet, only some of the resistant bacteria found in infants originated in their mothers. The rest were likely from the environment and other individuals.
"As a general rule, it could be said that all breastfeeding is for the better," said Microbiologist Katariina Parnanen, one of the study authors.
"The positive effect of breastfeeding was identifiable also in infants who were given formula in addition to breast milk. Partial breastfeeding already seemed to reduce the quantity of bacteria resistant to antibiotics. Another finding was that nursing should be continued for at least the first six months of a child's life or even longer. We have already known that breastfeeding is all in all healthy and good for the baby, but we now discovered that it also reduces the number of bacteria resistant to antibiotics," added Parnanen.
Bacteria resistant to antibiotics are among the greatest global threats to human health. According to estimates by previous research, bacteria and other micro-organisms resistant to antibiotics and other drugs will, by 2050, cause more deaths than cancer, since infections can no longer be effectively treated.