Take Home Test #1
1) What bacteria can be found associated with human breast milk in the typical, normal situation? Bacteria that can be found in human breast milk are very diverse. The typical bacteria that are found in human breast milk have the genus of: Bifidobacterium, Enterococcus, Kocuria, Lactobacillus, Lactococcus, Leuconostoc, Pediococcus, Propionibacterium, Rothia, Staphylococcus, Streptococcus, and Weissella (Leónides). According to Dr. Leónides and his expertise colleagues, the most popular of the bacteria that are found within human breast milk are: Staphylococcus, Streptococcus, Bifidobacterium, Enterococcus and Lactobacillus. The specific types of Staphylococcus found are: aureus, capitis, epidermidis, hominis. The specific types of Streptococcus found are: mitis, oris, parasanguis, salivarius. The specific types of Bifidobacterium are: adolescentis, bifidum, breve, breve, and longum. Next, the specific types of Enterococcus are: faecalis and faecium, Lastly, the specific types of Lactobacillus are: plantarum and fermentum. (Leónides) According to Dr. Fernandez Leónides and his collegues, studies have shown that certain bacteria in breast milk benefits infants. For example, Lactobacillus, Staphylococcus, Enterococcus, and Bifidobacterium, can sometimes benefit newborns through breastfeeding. The exposure to these bacteria can protect against diarrhea, respiratory diseases, and even reduce the risk of developing other diseases such as diabetes or obesity. However, in many individual cases however, Dr. Leónides points out that certain bacteria are highly personalized with particular individuals in their microbiome. 2) What is the source of these bacteria, where do they come from? The origin of the bacteria present in breast milk was traditionally believed to be from the breast milk that was the result of contamination with bacteria from the mother's skin or the infant's oral cavity. However, research by Dr. Leónides determined that infants nursing potentially cause the milk to flow back into the nipple and cause bacteria to form in the mammary ducts. This back flow causes an exchange of bacteria from the infant’s mouth into the mother’s mammary gland, however breast milk could often be the source of the bacteria. Certain bacterial phylotypes that are common in human breast milk such as Staphylococcus are present on the skin of adults (Leónides). This illustrates that the bacteria interacting with the skin contributes to the composition on the milk. This also addresses that the analysis of the skin must take into account that the skin often comes into contact with other bacteria. Bifidobacteria is an anaerobic genus, so it is unlikely that this particular bacteria is found on the skin. Research determined that some or most of this type of bacteria is located in the maternal gut. The bacteria reaches the breasts because dendritic cells penetrate the gut walls and take up non­pathogenic bacteria and push their way into the breasts (Leónides). Streptococcus species are one of the most abundant phylotype in colostrum and breast milk samples. These species are often located in the guts of mother’s and work their way into the breasts of women. According to Dr. Leónides and colleagues, this bacteria is moved from the gut to the mesenteric lymph nodes and mammary glands during late pregnancy. This species of bacteria often plays an important role in establishing salivary bacterial communities for infants (Leónides). Lactobacillus is commonly found in the bloodstream of healthy humans (Leónides). Long strains of Lactobacilli bacteria have been isolated from the breast milk. This bacteria is commonly associated with slightly higher birth weight and normal delivery (Leónides). Researchers concluded that this type of bacteria most likely enter through the bloodstream and work its way into the breasts. 3) What is mastitis? What can be that causative agent in humans? Mastitis is the inflammation of the breast tissues. Mastitis is usually caused by a blockage of the milk ducts or by bacterial infections (Better Health Channel). The blocked milk duct causes milk to pool in the breast, thus causing inflammation. A cracked nipple can allow bacteria to enter the breast and cause an infection. The causative agents in humans for mastitis pathogens are typically: yeasts, Streptococcus agalactiae, Staphylococcus aureus, and mycoplasma (Vine). Yeasts occur through transmission of contaminated needles or syringes. This type of mastitis is environmental and requires excessive antibiotic therapy (Vine). Streptococcus agalactiae is a gram­positive bacterium that inhabits ducts and cisterns of the gland. It causes inflammation that blocks the ducts, leading to decreased milk production. It is very sensitive to antibiotic treatment (Vine). Staphylococcus aurues is the leading cause of mastitis in the USA, because it causes peracute, acute, chronic, and subclinical mastitis. This type of bacteria is normally found on the skin of humans and enters through a crack in the nipple. The subclinical form produces many enzymes and toxins that are highly invasive and resist antibiotics. The result of the bacteria present in mastitis is that it decreases milk production and is very infectious to the breast tissues of humans (Vine). 4) Which bacteria are of concern from an infectious disease standpoint? The bacteria that are of concern of human breast milk usually include: Staphylococci, Streptococci, Corynebacteria, and gram­negative bacteria (Leónides). For Staphylococci, the certain types of the bacteria that can cause diseases and infections are: aureus and epidermidis (Vine). Staphylococci aureus has been considered one of the main etiological agents of acute mastitis. In addition, Staphylococci epidermidis is emerging as the leading cause of subacute and chronic mastitis both in human and veterinary medicine. Both of these two species of the bacteria can be resistant and immune to antibiotics, which make them dangerous to humans. If these two species of the bacteria are present in human breast milk, it is advised to discontinue breastfeeding immediately. These two types of Staphylococci often lead to mastitis. In addition, more infectious bacteria that are present in human breast milk are gram­negative bacteria. According to Tim Hall and colleagues, the infectious bacteria include E. coli and salmonella. E. coli poisoning often causes diarrhea in infants and in mothers (Hall). Salmonella often causes illnesses such as typhoid fever, paratyphoid fever, and foodborne illness. The salmonella is often ingested by the mother through contaminated foods, thus is transferred through the breast milk to the infant (Hall). 5) What modern biology technique is now used to give a better idea of what exactly is present in breast milk? To find bacteria in human breast milk, researchers are using culture­independent molecular techniques that are based on 16S rRNA genes, pyrosequencing, and PCR. They allow a diverse assessment of the human milk microbe. The use of such techniques confirmed the existence of Staphylococci and Streptococci, Bifidobacteria, and revealed the existence of DNA belonging to other bacterial groups, such as some Gram­negative bacteria (Leónides). In other studies, researchers are applying the genomics, metagenomics, transcriptomics, proteomics, and metabolomics methods to study human mammary microbiota (Leónides). The first study on human breast milk used microbial identification techniques based on pyrosequencing on certain regions of the bacteria in the 16S rRNA gene to characterize the bacterial communities present in milk samples. Pyrosequencing is a type of DNA sequencing that is repeated with each of the four letters until the DNA sequence of the single stranded template is determined (Leónides). 6) Why? The 16S rRNA gene sequence has become a more common technique to study bacterial phylogeny and taxonomy for many reasons. All of the reasons are: it is present in almost all bacteria, the function of the 16S rRNA gene has not changed over time, and 16S rRNA gene is large enough for sequencing (Abbott). According to Dr. Abbott, 16S rRNA sequencing is also becoming a more popular technique because the rRNA gene sequence data can be used for a multiplicity of purposes. One of the best uses of 16S rRNA gene sequence informatics is to provide genus and species identification for unknown bacteria. Results from studies suggest that 16S rRNA gene sequencing provides genus identification in most bacteria identifying cases (Abbott). Pyrosequencing is a type of DNA sequencing that is repeated with each of the four letters until the DNA sequence of the single stranded template is determined (Leónides). This is useful to finding bacteria in human breast milk because the DNA strands of the bacteria can easily be identified. 7) What additional bacteria have been found to be associated with the milk thanks to these techniques? The results of the 16S rRNA technique found the common Streptococcus and Staphylococcus bacteria. Of the hundreds of taxonomic unites that were detected in the milk the technique found more bacteria. The bacteria included were: Serratia, Pseudomonas, Corynebacteria, Ralstonia, Propionibacterium, Sphingomonas, and Bradyrhizobiaceae (Abbot). These 9 bacteria found in the breast milk represented approximately half of the microbial community observed from these techniques. Lactic acid bacteria (LAB) has also been found in breast milk through pyrosequencing. LAB often comprises the particular bacteria of: Lactobacillus, Lactococcus, and Streptococcus (Abbott). 8) Colostrum is very valuable. What is it, what does it contain? Colostrum, typically known as first milk, is the lacteal secretion of mammals (including humans), produced immediately before birth. Colostrum is a milky fluid and is typically present in breast milk for the first 24­48 hours after birth (Palmer). Colostrum is primarily used to feed newborns and provides essential nutrients for the immune system. (HealthyChildren.org). Colostrum is very beneficial to newborns for many reasons. First and most importantly, colostrum contains antibodies that protect the newborns from diseases (Palmer). However, the antibodies are small in number. These antibodies fight against disease causing agents such as bacteria and viruses. The antibody levels in colostrum are said to be 100 times higher in nutrition than regular cow’s milk (Web­MD). This means that colostrum is vital to newborns health. An example of a beneficial antibody that is present in colostrum is called "secretory immunoglobulin," also known as IGA (Palmer). This type of antibody helps protect the mucous membranes in the throat, lungs, and intestines of the infant (Science­Daily). In addition colostrum contains an antibody called leukocytes. Leukocytes, white blood cells, are present in large numbers and begin protecting infants from harmful viruses and bacteria. When associated with colostrum, leukocytes help prevent infant’s bodies from jaundice by reducing the volume of red blood cells. (Science­Daily). Secondly, colostrum contains high concentrations of nutrients. Colostrum is high in carbohydrates, high in protein, and low in fat (Healthy Children). The colostrum being low in fat is beneficial to newborns because they have difficulty digesting fat. Colostrum delivers nutrients in very concentrated low­volume forms. This is beneficial to newborns because they have small digestive systems, so they can easily consume the colostrum (Science Daily). Typically, colostrum is healthier than regular milk. 9) What does colostrum tell you about microbes that mom has encountered? The breast milk in the mother is effected by the microbes that are present in the mother. According to the American Journal of Clinical Nutrition, in many samples taken of colostrum, more than 700 species of microorganisms have been found (Cabrera­Rubio). The most common bacteria found in the colostrum samples were Weissella, Leuconostoc, Staphylococcus, Streptococcus and Lactococcus. All of these bacteria can illustrate what the mother has encountered. Many of these types of bacteria can be found in the gut of the mother. This could mean that the mother had eaten food that contained the bacteria (Cabrera­Rubio). Research has also shown that the heavier the mother, the fewer the bacteria (Cabrera­Rubio). In Cabrera­Rubio’s study, he reveals that the milk of overweight mothers or those who put on more weight than recommended during pregnancy contains less species of bacteria. In the study, it was determined that mothers who had a vaginal birth were not as rich in bacteria as mother’s who had to have a caesarean. The results of the lab suggest that hormones do play a role in the microbes that are present in colostrum.

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