Microbiota in Breast Milk of Chinese Lactating Mothers

Abstract

The microbiota of breast milk from Chinese lactating mothers at different stages of lactation was examined in the framework of a Maternal Infant Nutrition Growth (MING) study investigating the dietary habits and breast milk composition in Chinese urban mothers. We used microbiota profiling based on the sequencing of fragments of 16S rRNA gene and specific qPCR for bifidobacteria, lactobacilli and total bacteria to study microbiota of the entire breast milk collected using standard protocol without aseptic cleansing (n = 60), and the microbiota of the milk collected aseptically (n = 30). We have also investigated the impact of the delivery mode and the stage of lactation on the microbiota composition. The microbiota of breast milk was dominated by streptococci and staphylococci for both collection protocols and, in the case of standard collection protocol, Acinetobacter sp. While the predominance of streptococci and staphylococci was consistently reported previously for other populations, the abundance of Acinetobacter sp. was reported only once before in a study where milk collection was done without aseptic cleansing of the breast and rejection of foremilk. Higher bacterial counts were found in the milk collected using standard protocol. Bifidobacteria and lactobacilli were present in few samples with low abundance. We observed no effect of the stage of lactation or the delivery mode on microbiota composition. Methodological and geographical differences likely explain the variability in microbiota composition reported to date.

Microbial Communities in Human Milk Relate to Measures of Maternal Weight

“…Differences by delivery mode were observed in a study of milk samples from 80 women in four countries on three continents, but the effect was primarily among the subgroup of 20 Spanish women (Kumar et al, 2016). Consistent with our findings, a recent study of human milk from 60 Chinese women across three time points and two collection techniques (Sakwinska et al, 2016) and one studying 109 American mothers (Pannaraj et al, 2017) did not observe an association of cesarean section delivery with microbial populations in human milk. Other studies suggesting an influence of delivery mode on human milk microbiota (Cabrera-Rubio et al, 2012;Khodayar-Pardo et al, 2014;Cabrera-Rubio et al, 2016) were very small, with 32 subjects or fewer.…”

“…Many samples in our study contained Acinetobacter. This may be partially attributable to the collection method that did not involve sterilization of the breast skin prior to collection using a breast pump (Sakwinska et al, 2016), which we chose in order to have a clearer understanding of infants' actual exposures. However, many subjects had very low abundances of this microbe despite the same collection method, so factors other than this likely contribute to its presence.…”

“…Additionally, women who delivered prematurely show lower abundance of Bifidobacterium (Khodayar-Pardo et al, 2014). However, other studies have not observed associations of delivery mode or gestational age with breast milk microbiota (Sakwinska et al, 2016;Urbaniak et al, 2016;Pannaraj et al, 2017;Ojo-Okunola et al, 2019). Relatively small sample size or unmeasured confounding factors in prior work may account for inconsistent results across studies and indicates the need for further investigation in larger studies.…”

“…Butyrate is a short chain fatty acid of microbial metabolic origin that is known to be important for the integrity of the gut epithelial barrier and is protective against many intestinal and systemic diseases (Canani et al, 2011). Preliminary small studies using 16S rRNA gene sequencing and metagenomics approaches to assess breast milk microbial composition have reported that Streptococcus, Staphylococcus, Pseudomonas, Bacteroides, Acinetobacter, and others comprise the core breast milk microbiome, whereas Bifidobacterium and Lactobacillus abundances are comparatively low (Hunt et al, 2011;Jost et al, 2013;Ward et al, 2013;Jiménez et al, 2015;Sakwinska et al, 2016;Urbaniak et al, 2016;Murphy et al, 2017). Clusters of breast milk microbiota have been reported, often defined by the abundance of Staphylococcus, Streptococcus, and Pseudomonas, Enterobacteriaceae, and other rarer bacteria (Li et al, 2017;Biagi et al, 2018;Moossavi et al, 2019b).…”

Determinants and Duration of Impact of Early Gut Bacterial Colonization

“…In a Chinese study of the microbiota in breast milk of mothers measured from birth to 2 months of age, the milk was expressed with or without aseptic cleaning of the breast before collection. There was much greater diversity of the breast milk microbiome of those who did not clean the breast suggesting a significant contribution from the skin of the breast and they found no effect of stage of lactation or delivery mode [20] .…”