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The ‘microbiome’ contains all the bacteria, fungi and viruses that live on and in you. It is estimated that for every one of our cells there exist three microbes! Each part of our bodies creates a mini habitat for these residents to grow, and so distinct microbial communities are present all over. In fact, one of the most diverse and important habitats is in our guts, where approximately 10 trillion bacteria are helping us to fulfil a range of functions, from digesting food to producing essential vitamins [1].


The first bacteria introduced to our gut microbiome are critical to developing our immune system and keeping disease-causing microbes at bay. One of the key contributors to the infant gut microbiome is breast milk. Over 200 species of bacteria have been discovered living in milk, and it has been estimated that they contribute 40% to the emerging infant gut community [2]. Many variables can influence the breast milk microbiome, including age, geography and genetics. However, one of the most influential factors is antibiotic usage.


Antibiotics are one of the most prescribed drugs during lactation [3]. Mothers often require antibiotics to treat mastitis or while recovering from a C-section delivery. Antibiotics stop infections by blocking vital processes in bacteria or damaging structures within the bacterial cell. Most antibiotics are safe for breastfeeding mothers, except for a few (e.g. quinolones, chloramphenicol, and aminoglycosides during the early postnatal period) [4]. The general rule is if it is safe for the infant to use, then it is safe for the mother to take while breastfeeding.


In western countries, up to 35% of women are exposed to an antibiotic during pregnancy and delivery [5]. In fact, antibiotics make up the vast majority (80%) of the total drugs prescribed to pregnant women [6]. Whilst antibiotics are crucial for killing disease-causing bacteria, they also kill a broad spectrum of beneficial microbes. Additionally, antibiotic usage can actively increase the number of non-beneficial bacteria which carry antibiotic-resistant genes [7]. Even a short course of antibiotics can alter the number of key microbes in breast milk, and this can be detected for eight weeks. While this is a large limitation of antibiotics, it is still imperative that mothers take them when prescribed. 


With this in mind, what can breastfeeding mothers do to limit the effect antibiotics have on their microbiomes?


1. Broaden your diet.

By eating a broader range of food, you will have access to more nutrients. This will provide a better habitat for the bacteria to grow again. In particular, eating fermented foods (check whether they are safe to eat whilst breastfeeding!) such as yoghurt, pickles, and kvass has been shown to accelerate beneficial microbiome development [8]

2. Avoid excessive cleaning

As your antibiotics are already killing a large range of bacteria, over-usage of multipurpose cleaning products and antibacterial wipes will also make your pool of re-colonising beneficial bacteria smaller [9]! Try to limit the use of cleaning products to once a week and use soap and water instead.

3. Don’t be discouraged.

Your milk still contains critical immune cells for protecting your baby and excellent nutrition that cannot be replicated anywhere else!


Finally, it could be worth buying a probiotic while taking an antibiotic course. The jury is still out on which probiotics are the most effective [10]. We recommend finding a brand that has either been recommended by a healthcare provider or previously used in a clinical trial. 


At Boobybiome, we are using breast milk as our guide to developing unique infant bacterial products for developing these microbiome communities. Our products are developed from rigorous scientific testing and designed to mimic the breast milk microbiome. Our products will be critical in helping bacteria in the infant's gut when antibiotics are prescribed. Watch this space!

What do we know about the breast milk microbiome and antibiotic usage?


By Lydia Mapstone and Eileen Hahn.

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