Bacterial analysis of breast milk: a tool to differentiate Raynaud's phenomenon from infectious mastitis during lactation

Human Milk Microbiota in an Indigenous Population Is Associated with Maternal Factors, Stage of Lactation, and Breastfeeding Practices

BACKGROUND

Human milk contains a diverse community of bacteria that are modified by maternal factors, but whether these or other factors are similar in developing countries has not been explored. Our objective was to determine whether the milk microbiota was modified by maternal age, BMI, parity, lactation stage, subclinical mastitis (SCM), and breastfeeding practices in the first 6 mo of lactation in an indigenous population from Guatemala.

METHODS

For this cross-sectional study, Mam-Mayan indigenous mothers nursing infants aged <6 mo were recruited. Unilateral human milk samples were collected (n = 86) and processed for 16S rRNA sequencing at the genus level. Microbial diversity and relative abundance were compared with maternal factors [age, BMI, parity, stage of lactation, SCM, and 3 breastfeeding practices (exclusive, predominant, mixed)] obtained through questionnaires.

RESULTS

Streptococcus was the most abundant genus (33.8%), followed by Pseudomonas (18.7%) and Sphingobium (10.7%) but relative abundance was associated with maternal factors. First, Lactobacillus and Streptococcus were more abundant in early lactation whereas the common oral (Leptotrichia) and environmental (Comamonas) bacteria were more abundant in established lactation. Second, Streptococcus,Lactobacillus,Lactococcus,Leuconostoc, and Micrococcus had a higher abundance in multiparous mothers compared with primiparous mothers. Third, a more diverse microbiota characterized by a higher abundance of lactic acid bacteria (Lactobacillus,Leuconostoc, and Lactococcus), Leucobacter, and Micrococcus was found in mothers with a healthy BMI. Finally, distinct microbial communities differed by stage of lactation and by exclusive, predominant, or mixed breastfeeding practices.

CONCLUSION

Milk bacterial communities in an indigenous community were associated with maternal factors. Higher microbial diversity was supported by having a healthy BMI, the absence of SCM, and by breastfeeding. Interestingly, breastfeeding practices when assessed by lactation stage were associated with distinct microbiota profiles.

Host Microbe Interactions in the Lactating Mammary Gland

The bacteria present in human milk constitute the human milk microbiome (hMM). Both the older culture-based work and the more recent studies using molecular detection of bacterial DNA have reached similar conclusions: the hMM mostly consists of commensal staphylococci such as Staphylococcus epidermidis, and streptococci. The prevalence of other bacterial groups such lactobacilli varies widely, while the abundance and prevalence of bifidobacteria is generally low. Recently, the hMM became accepted as a part of a physiologically normal state with suggested potential health benefits. Most research on the hMM has focused on its composition and potential effect on the breastfed infant. A major role as a microbiome inoculum for the infant gut has been proposed, but remains to be clearly demonstrated. Herein, we also discuss the emerging connection between the hMM and mammary gland physiology and lactation. Similarities between the mammary gland and mucosal interfaces are considerable, and in particular mucosal-like immune attributes of mammary gland. The potential role of hMM-host interactions in the mammary gland in maternal health is explored with a primary focus on lactational mastitis.

The microbiology and treatment of human mastitis

Mastitis, which is generally described as an inflammation of breast tissue, is a common and debilitating disease which frequently results in the cessation of exclusive breastfeeding and affects up to 33% of lactating women. The condition is a primary cause of decreased milk production and results in organoleptic and nutritional alterations in milk quality. Recent studies employing culture-independent techniques, including metagenomic sequencing, have revealed a loss of bacterial diversity in the microbiome of mastitic milk samples compared to healthy milk samples. In those infected, the pathogens Staphylococcus aureus, Staphylococcus epidermidis and members of corynebacteria have been identified as the predominant etiological agents in acute, subacute and granulomatous mastitis, respectively. The increased incidence of antibiotic resistance in the causative species is also a key cause of concern for treatment of the disease, thus leading to the need to develop novel therapies. In this respect, probiotics and bacteriocins have revealed potential as alternative treatments.

Mammary microbiota of dairy ruminants: fact or fiction?

Explorations of how the complex microbial communities that inhabit different body sites might contribute to health and disease have prompted research on the ways the harmonious relationship between a host and its microbiota could be used to keep animals healthy in their production conditions. In particular, there is a growing interest in the bacterial signatures that can be found in the milk of healthy or mastitic dairy cows. The concept of sterility of the healthy mammary gland of dairy ruminants has been challenged by the results of studies using bacterial DNA-based methodology. The newly obtained data have led to the concept of the intramammary microbiota composed of a complex community of diverse bacteria. Accordingly, mammary gland infections are not mere infections by a bacterial pathogen, but the consequence of mammary dysbiosis. This article develops the logical implications of this paradigm shift and shows how this concept is incompatible with current knowledge concerning the innate and adaptive immune system of the mammary gland of dairy ruminants. It also highlights how the concept of mammary microbiota clashes with results of experimental infections induced under controlled conditions or large field experiments that demonstrated the efficacy of the current mastitis control measures.

Impact of mode of delivery on the milk microbiota composition of healthy women

Breast milk constitutes one of the most important sources of postnatal microbes. However, the influence of perinatal factors on the milk microbiome is still poorly understood. The aim of our study was to assess the impact of mode of delivery on the microbiome composition and diversity present in breast milk of healthy mothers. Mature milk samples (n=10) were taken from mothers after 1 month of exclusively breastfeeding. Microbiomes from milk samples were analyzed with 16S ribosomal RNA gene pyrosequencing and targeted quantitative polymerase chain reaction (PCR). Despite inter-individual variability in bacterial composition, The Principal Coordinates Analysis clearly separated milk microbiome from mothers with vaginal delivery (n=6) from those who undergo C-section (n=4). In addition, higher bacterial diversity and richness was found in milk samples from vaginal deliveries. Quantitative PCR data showed that higher levels of Bifidobacterium spp. were related significantly to lower levels of Staphylococcus spp. Despite the low sample size, our data suggest that mode of delivery has an important impact on milk microbiome composition. Further studies with larger sample sizes are needed to confirm these results and to understand the biological effects of C-section associated microbes on infant's health.

Gut microbiota: a source of novel tools to reduce the risk of human disease?

Modern civilization is faced with a progressive increase in immune-mediated or inflammatory health problems such as allergic disease, autoimmune disorders, and obesity. An extended version of the hygiene hypothesis has been introduced to emphasize the intimate interrelationship among diet, the immune system, microbiome, and origins of human disease: the modern infant, particularly when delivered by cesarean section and without the recommended exclusive breastfeeding, may lack sufficient stimulation of the mucosal immune system to generate a tolerogenic immune milieu and instead be prone to develop chronic inflammatory conditions. These deviations may take the form of allergic or autoimmune disease, or predispose the child to higher weight gain and obesity. Moreover, evidence supports the role of first microbial contacts in promoting and maintaining a balanced immune response in early life and recent findings suggest that microbial contact begins prior to birth and is shaped by the maternal microbiota. Maternal microbiota may prove to be a safe and effective target for interventions decreasing the risk of allergic and noncommunicable diseases in future generations. These results support the hypothesis that targeting early interaction with microbes might offer an applicable strategy to prevent disease.

The infant microbiome development: mom matters

The infant microbiome plays an essential role in human health and its assembly is determined by maternal-offspring exchanges of microbiota. This process is affected by several practices, including Cesarean section (C-section), perinatal antibiotics, and formula feeding, that have been linked to increased risks of metabolic and immune diseases. Here we review recent knowledge about the impacts on infant microbiome assembly, discuss preventive and restorative strategies to ameliorate the effects of these impacts, and highlight where research is needed to advance this field and improve the health of future generations.

Probiotics for human lactational mastitis

The use of culture-dependent and -independent techniques to study the human milk microbiota and microbiome has revealed a complex ecosystem with a much greater diversity than previously anticipated. The potential role of the milk microbiome appears to have implications not only for short- and long-term infant health but also for mammary health. In fact, mammary disbiosis, which may be triggered by a variety of host, microbial and medical factors, often leads to acute, subacute or subclinical mastitis, a condition that represents the first medical cause for undesired weaning. Multiresistance to antibiotics, together with formation of biofilms and mechanisms for evasion of the host immune response, is a common feature among the bacterial agents involved. This explains why this condition uses to be elusive to antibiotic therapy and why the development of new strategies for mastitis management based on probiotics is particularly appealing. In fact, selected lactobacilli strains isolated from breast milk have already shown a high efficacy for treatment.

Cultures of Holder-pasteurized donor human milk after use in a neonatal intensive care unit

OBJECTIVE

Current guidelines state that human milk, once thawed, should be kept in a refrigerator for only 24 hours. We cultured Holder-pasteurized donor human milk (DHM) after thawing and refrigeration under clinical conditions.

STUDY DESIGN

Bottles of pasteurized DHM were thawed and used in a regional level 3 neonatal intensive care unit (NICU) in standard clinical fashion and kept refrigerated when not in use. Once no longer needed clinically, aliquots were cultured for bacteria.

RESULTS

In total, 30 bottles were returned for culture; six were excluded from analysis because human milk fortifier had been added, and two had been left out of the refrigerator. The remaining 22 bottles were culture-negative after having been thawed for 7-122 hours.

CONCLUSIONS

DHM without additives was culture-negative for 24 hours or longer after thawing and routine NICU handling. These data indicate that unfortified Holder-pasteurized DHM handled appropriately and refrigerated remains sterile for 24 hours after thawing and perhaps longer. Further study is needed to confirm this.

Mastitis: comparative etiology and epidemiology

Mastitis is broadly defined as the inflammation of the mammary gland; however, the concept of mastitis is customized to address its social and clinical impact in the case of humans and the health, welfare, and economic consequences for other mammals. There are many microbial, host, and environmental factors that influence the development of mastitis. Some are common to all mammals as well as inherent to each species. Together these factors influence the most prevalent etiological agents for each species and might determine the possibility of interspecies transmission with its consequences to public health. The present review will summarize and compare reports on mastitis etiology and its epidemiology in humans and food animal species.

Analysis of bacterial and fungal communities in Japanese- and Chinese-fermented soybean pastes using nested PCR-DGGE

The microbial diversity of Japanese- and Chinese-fermented soybean pastes was investigated using nested PCR-denaturing gradient gel electrophoresis (DGGE). Five Japanese-fermented soybean paste samples and three Chinese-fermented soybean paste samples were analyzed for bacteria and fungi. Extracted DNA was used as a template for PCR to amplify 16S rRNA and 18S rRNA genes. The nearly complete 16S rRNA and 18S rRNA genes were amplified using universal primers, and the resulting products were subsequently used as a template in a nested PCR to obtain suitable fragments for DGGE. Tetragenococcus halophilus and Staphylococcus gallinarum were found to dominate the bacterial microbiota in Japanese samples, whereas Bacillus sp. was detected as the predominant species in Chinese samples. DGGE analysis of fungi in soybean pastes determined the presence of Aspergillus oryzae and Zygosaccharomyces rouxii in most of the Chinese and Japanese samples. Some differences were observed in the bacterial diversity of Japanese- and Chinese-fermented soybean pastes.